The leading ladies of all three...
In the Epilogue of Sheridan's The Rivals, Mrs. Bulkley declares,
Man's social happiness all rests on us:
Through all the drama—whether damn'd or not—
Love gilds the scene, and women guide the plot.
From every rank obedience is our due—
The leading ladies of all three plays do, indeed, "guide the plot[s]" of the three plays under discussion. Here are some of their idealistic and realistic traits:
For the most part, Lydia remains ridiculously idealistic throughout the play, from her initial sending of her servant Lucy out for romantic novels such as The Fatal Connexion so that she can model her life upon them, She refuses to marry within her social realm, preferring the penniless Ensign Beverly. In her illusory state, she even goes so far as to create conflicts so that they can be romantically resolved as in her novels. She tells Julia that she was afraid that she and Beverly would never have a lovers' quarrel, so she has fabricated one:
I wrote a letter to myself, to inform myself that Beverley was at that time paying his addresses to another woman. I signed it your friend unknown, showed it to Beverley, charged him with his falsehood, put myself in a violent passion, and vowed I'd never see him more.
So idealistic is Lydia that when she learns the true identity of Beverly as the same man (Jack Absolute) that her aunt and Sir Anthony, his father desire her to marry, she still rejects Jack even though she will lose her inheritance. It is not until he informs her that he is in a duel, that she accepts him because he can, then, remain her romantic hero.
Yet, ironically, Lydia is realistic about her friend Julia and the relationship with Faulkland, as she informs the unrealistic Julia of the faults of her lover,
...the jealousy of this ungrateful Faulkland, who will ever delay assuming the right of a husband, while you suffer him to be equally imperious as a lover.
When Lydia speaks to Julia about her jealous love, Julia is too idealistic about him to perceive the truth,
No, Lydia, he is too proud, too noble to be jealous; if he is captious, 'tis without dissembling; if fretful, without rudeness.
Truly, Julia is ideal of a female lover; for, she is loyal and steadfast and even tender in her love for Faulkland, perceiving him with a lover's eyes. Yet, as she overlooks his faults, she does scold him and tells him she will set him free in Act III, Scene 2,
Let us be free as strangers as to what is past: my heart will not feel more liberty!
Fortunately, Faulkland realizes his folly and entreats Julia to take him back.
In her idealistic concept of grief, Olivia has "abjured the sight/And company of men" (1.2.40) for seven years following the death of her dear brother; consequently, she refuses the suit of the Duke Orsino. Then, in Scene 5 of Act I, she suddenly becomes infatuated with Cesario when he calls upon her to plea Orsino's suit:
Methinks I feel this youth's perfection
With an invisible and subtle stealth
To creep in at mine eyes. Well, let it be. (1.5.230-233)
Also, in her unrealistic and idealistic view of life, Olivia readily accepts what she feels for Cesario as part of her fate, having said, "Well, let it be." In her idealism, she surrenders to fate.
Fate, show thy force. Ourselves we do not owe:
What is decreed must be; and be this so! (1.5.310-11).
On the other hand, Olivia is realistic as she is well aware of what goes on in her household. While she does not approve of Sir Toby's excessive libation, she tolerates him; furthermore, after he and the others trick and ridicule Malvolio, she makes efforts to bring him back into the wedding party at the play's end.
In her realistic awareness of her condition upon arriving in Illyria, Viola agrees to follow the Captain's suggestions and disguise herself as Cesario and serve the Duke until she can learn what has become of her shipwrecked twin brother Sebastian. After the Duke Orsino sends her as Cesario to woo Olivia, the results are not as expected as Olivia falls in love with Cesario. Viola realistically assesses the situation,
She loves me sure....
Poor lady, she were better love a dream.
Disguise, I see, thou art a wickedness (2.2.17-22)
Viola rarely, if ever, displays idealism, although her hope of finding her brother is, perhaps, idealistic. Then, too, she may be idealistic in believing that Orsino will love her dressed as a man because she fails to reveal her true identity at the end of the play.
Comedy of Errors
Adriana and Luciana
In Act II, Scene 2, the sisters discuss husbands, and Luciana responds very idealistically to her sister's question,such as
Why should their liberty than ours be more? [Adriana]
Because their business still lies out o'door.... [Luciana]
There's nothing situate under heaven's eye
But hath his bound, in earth, is sea, in sky....
Man, more divine, the master of all these,
Lord of the wide world and wild wat'ry sea,
Imbued with intellectual sense and souls....(2.1.15-22)
Adriana's reply to Luciana is harshly realistic:
They can be meek that have no other cause....
So thou, that hast no unkind mate to grieve thee...(2.1.33-34)
Later, however, Luciana becomes more negative in her feelings about husbands when Antipholus of Syracuse (whom she mistakes for Adriana's husband) tries to court her. Mistakenly, Luciana thinks Antipholus is being unfaithful to his wife, and she reports his proposition to her sister.
Because this action and mood of this play is based so much upon mistaken identities, it is difficult to judge the characters' perspectives since they are usually predicated upon false assumptions of identity in the beginning.