Emilia is a lower-class, rather earthy woman who is married to Iago and serves as a personal maid to Desdemona. She is devoted to her mistress. She exists mainly for dramatic purposes. She and Desdemona exchange thoughts, confidences, and factual information in their dialogue, all of which make it convenient for Shakespeare to advance his story. Without Emilia he might have had to resort to writing soliloquies for Desdemona. Emilia is loyal to her husband and tries to please him, although he doesn't deserve to be loved by anyone. It is she who steals the handkerchief and gives it to Iago, who uses it to augment Othello's jealousy and to save his own skin by providing the tangible proof of adultery that Othello demands. Finally, it is Emilia who causes Iago's exposure and downfall by informing everyone that her husband was behind the theft of the handkerchief and assuring everyone that Desdemona was entirely faithful to her husband. Emilia's uncontrollable grief in the last scene of the play helps to demonstrate her complete sincerity as well as to enhance the emotional effect of the finale.
first of all when she finds a love gift handkerchief of Desdemona , she gives this to Iago to make him pleased, this was her first contribution to the play' tragedy.
secondly she does not tell Othello about the evil intentions of her husband till he kills Desdemona. this thing create a tragic effect in drama.