husband's priorities first, Emilia still proves loyal to Desdemona

As one can see, Emilia's contradictory nature contributes to her complexity. She seems to deceive others because she does not broadcast her thoughts and emotions as others do. Her intelligence is overlooked by even her husband, as he does not assume she will figure out his plan. 

Emilia, who is Iago's wife and Desdemona's handmaid, serves to advance the plot of Othello in significant and dramatic ways. Emilia serves as one of two foils to Desdemona—the other is Bianca. Both Emilia and Bianca exhibit beliefs or actions that directly oppose the actions of Desdemona. Emilia is Desdemona's confidante, and the two share a special bond. The two women have divergent views on their own married lives—Emilia can't handle that she is stuck in a marriage to Iago, while Desdemona is wildly and even blindly in love with Othello. Emilia is ultimately proved untrustworthy, despite the actions she takes to decry Iago later.

In the meantime, Emilia's closeness to Desdemona presents the perfect opportunity for her to carry out Iago's orders to collect Desdemona's handkerchief, which results in charges against Desdemona for infidelity and Desdemona's ultimate death. Iago stealthily plants the handkerchief in Cassio's room, fostering a view of Desdemona as unfaithful. The experience of losing Desdemona through her servility to Iago—an evil and cruel man—eventually prompts Emilia to throw off Iago's authority, which reflects ironically on Iago's own words: "nor can all masters be truly followed." In this way, Emilia overcomes her subordinate role to Iago and gains a measure of autonomy, even though it results in her death—Iago kills her for exposing his plot. Her death is not in vain, however, as Iago is exposed and Desdemona's reputation is posthumously restored.

This is a complicated question, mainly because the theoretical framework found in Aristotle's Poetics doesn't really address minor characters. Aristotle's understanding of tragedy was based on classical Greek plays which had a single protagonist (which would be Othello in this play), an antagonist (Iago), minor characters (everyone else), and a chorus. Aristotle's description of the action of a play (hamartia, reversal, recognition scene) all applied to events happening to the protagonist. Thus one can only apply Aristotle to the character Emilia by doing an analysis of what she contributes to the narrative of Othello, or by moving beyond Aristotle's Poetics and using his Rhetoric to analyze the persuasive nature of Emilia's speeches.

The Greek term "hamartia" is a noun deriving from the verb "hamartein" meaning to miss a mark, as in archery when an arrow misses. There is a sense of a mistake which is irrevocable, like an arrow released that cannot be put back in a bow. In the case of Othello, it is the belief that Desdemona is unfaithful and the decision to act upon that belief. What makes this a tragic character flaw is that (1) it happens to an otherwise great or admirable character and (2) it flies in the face of advice from other characters, and the protagonist has many opportunities to turn back from this course before the irrevocable action. Emilia is one of the characters who tries to persuade Othello to turn his back on his jealousy and trust his wife:

I durst, my lord, to wager she is honest,
Lay down my soul at stake: if you think other,
Remove your thought; it doth abuse your bosom. ...

Even though Othello trusts Emilia's honesty and moral character at this point, he believes that she is not very smart ("a simple bawd") and herself has been duped.

Emilia's final speech in Act IV shows her not, in fact, to be simple, but to be clear-sighted and intelligent, analyzing marriage from a cool logical perspective, using rhetorical devices mentioned in Aristotle's Rhetoric such as the topos of lesser and greater, inductive reasoning from examples, and reasoning by analogy.

Emilia's action in taking the handkerchief enables the castastrophe, the downfall of Othello. In the climax of the play, her main function is to prove Desdemona's innocence and Iago's guilt by revealing the true history of the handkerchief. 

Rhetorically, what is most interesting about Emilia's lines in the final scene is that although she does evoke pity for Desdemona, she actually uses arguments from logos even more than pathetic arguments. Rather than being a "simple bawd" she shows herself an intelligent woman with a great deal of common sense, despite having been temporarily deceived by the cunning Iago.

At the start of the play, Emilia appears to be subservient and manipulated by her husband, Iago, but by the end she has gained in self-confidence and has seen him for the villain he is; finally, she denounces him and reveals his evil to the world. Initially, Emilia does what Iago bids her, despite his lack of warmth to her. Although she feels guilty, she steals Desdemona’s handkerchief for Iago to use as evidence of Desdemona’s infidelity. The audience can understand that Emilia simply wants to please Iago in doing this, saying "I nothing but to please his fantasy," which she quickly regrets when he fails to praise her and she feels remorseful about deceiving her friend Desdemona. It is this friendship that seems to move Emilia to find her moral compass, even though she becomes bitter about her marriage.

 By the end of the play, the submissive Emilia criticizes men in a way that would have been seen as powerful and almost heretical to the Jacobean audience of Shakespeare’s time.  She says "But I do think it is their husbands’ faults/If wives do fall," thus blaming men for leading women astray, which would be unusually opinionated for a woman in the male-dominated patriarchal society of the time. It is ironic that Iago underestimates Emilia, as she finally exposes him for being the cause of so many deaths. Iago has made a mistake based on his own lack of morality and assumptions of others; he never thought that Emilia would betray him and sacrifice herself to "love and duty," which is precisely what she does.

You seem to have sufficiently covered Emilia's responsibilities for the murder of Desdemona. However, you might consider discussing how she could have been responsible for Othello's subsequent suicide. She is not terribly eloquent until after she discovers that Othello has killed Desdemona. Then she becomes voluble and eloquent in defending her dead mistress, proving her innocence, reminding Othello of his love for her and hers for him, saying everything possible to remind him of his guilt, his gullibility, and his irretrievable loss. This tirade begins with the following dialogue in Act 5, Scene 2:

OTHELLO
She's like a liar gone to burning hell!
'Twas I that killed her.
EMILIA
O, the more angel she,
And you the blacker devil!
OTHELLO
She turned to folly, and she was a whore.
EMILIA
Thou dost belie her, and thou art a devil.
OTHELLO
She was false as water.
EMILIA
Thou art rash as fire to say
That she was false. O, she was heavenly true!

Othello felt bad enough even before he killed his wife. He feels much worse afterward. Then Emilia relentlessly abuses him verbally, even when he threatens to kill her if she won't shut up. Then she exposes Iago's villainy to give the final proof that Othello killed a wife who was totally pure and innocent.

Emilia plays an essential part in the last scene of the play. It is in her dialogue with Othello after he has murdered Desdemona that Emilia contributes the most to the tragic ending. After all, this is not Desdemona's tragedy but Othello's, since the play is about Othello, the Moor of Venice. You could strengthen the conclusion of your paper by quoting Emilia verbatim and explaining how her words are torturing Othello and possibly helping to motivate him to commit suicide.

Emilia was an innocent victim of Iago. It would be much harder to show her as being responsible for Desdemona's death than to show her responsibility for Othello's suicide.

Characters in a play generally function to forward the plot, explain what is going on, and illuminate the drama's themes. Emilia does all three, making her a significant character in Othello.

Shakespeare needed somebody to steal Desdemona's handkerchief so that Iago could bring his evil plot to fruition. As Iago's wife and Desdemona's attendant, Emilia is the perfect person to fulfill this task. She doesn't know why Iago wants it, but she allows him to browbeat her into doing the deed. Ironically, even though she loves Desdemona and is loyal to her, she becomes an instrument in her destruction.

Emilia also functions at the play's end to explain what has happened. As she realizes she was used as a tool by her husband and manipulated into betraying Desdemona, her integrity causes her to expose Iago's hand in the plot. He kills her, but too late—the truth is out.

Importantly, Emilia illuminates the theme of good versus evil. She is a foil or contrast to her husband. Unlike Iago, she is capable of friendship, loyalty, and love, caring deeply for Desdemona and appreciating her goodness. She is a practical, and in some ways cynical person, but at heart she is ethical. The fact that even she, Iago's wife, is deceived by him, makes it more plausible that Othello also fell for his tricks and manipulations.

Emilia is Iago’s wife and Desdemona’s maid. By nature she is a straightforward, outspoken person. However, she is placed in a complicated position because she is torn between her loyalty to her husband and to her mistress, of whom she is very fond. Emilia plays a key role in the plot at two crucial points. It is she who finds the dropped handkerchief and turns it over to Iago, not suspecting how he intends to use it. In addition, at the end she realizes the full extent of Iago’s perfidy and exposes his lies, which leads to his arrest but at the cost of her life. In a parallel with Othello’s killing Desdemona, her husband also kills her.

Although Emilia knows that Iago has a dark side, she does not realize until it is too late that he has become obsessed with ruining Othello. His jealousy has been a problem in their marriage, and part of his underlying motivation seems to be his mistaken conviction that she had slept with Othello.

Emilia offers her insights into male jealousy in a monologue she delivers within a conversation with Desdemona (Act IV, Scene 3). Emilia’s opinion is that the husband is to blame if the wife has sex with another man. Although she does not explicitly state that Iago has done some of the things she mentions, it seems she is drawing on her own experience. She hypothetically mentions their ignoring their responsibilities, acting jealous, and not providing adequate financial support. She suggests they commit physical violence: “say they strike us….” The speech opens with her laying the “fault” on the husbands, and concludes in the same vein:

Then let them use us well: else let them know,
The ills we do, their ills instruct us so.