Romeo and Juliet have spent their wedding night together, and they're both trying to put off Romeo's departure in their discussion of whether the lark or the nightingale is singing. Their night together has cemented their relationship, and we see how much their love has matured. They are naturally upset that they cannot be together for now. As Romeo leaves, Juliet looks down at him and has a sense of foreboding that she sees Romeo in a tomb. When her parents tell Juliet of her impending marriage to Paris, she then becomes desperate because her parents and the Nurse have turned their backs on her. She's also determined to find a way out, or she will kill herself.
Juliet's parents think they are doing Juliet a favor, but when she tells her mother she doesn't want to marry Paris, Lady Capulet becomes so angry that she tells her husband she wishes Juliet was dead. Lord Capulet rants and raves saying he'll throw Juliet out to beg in the streets. Her mother displays coldness to Juliet, and her father is outraged that Juliet would dare to defy him.
The Nurse even turns on Juliet, telling her to go ahead and marry Paris, knowing she's already married to Romeo. Juliet loses total confidence in the Nurse and is hurt by her suggestion since the Nurse has always been there for her, even helping Juliet to marry Romeo.
You have a mixed bag of emotions in this scene from the different characters. Most of all, Juliet changes into a woman of determination and strength of character.
Grief, misunderstanding, and desperation are the words I would use to characterize 3.5. This scene is the aftermath of Romeo's slaying of Juliet's cousin, Tybault and his subsequent banishment from Verona.
Romeo has made it back to Juliet's home and is in her bed. Daylight is rapidly approaching and he knows he must go. He says he hears the call of the lark, that bird of the morn. But Juliet insists that it is a nightingale they hear, hoping to prolong their time together.
Lady Capulet finds her daughter in bed (after Romeo's exit) and still thinks Juliet mourns for Tybault. Her father is not impressed by his daughter's pain and inists that she get over it and go ahead with the marriage to Paris. Juliet's nurse comes to her defense ("You are to blame, my lord, to rate her so" 3.5.169)
Juliet in the conclusion of this scene feels complete desperation. She will go to the Friar, in wild hopes that he can remedy the situation. She urges, "Go, counsellor. / Thou and my bosom henceforth shall be twain. / I'll go to the Friar to know his remedy. / If all else fail, mysefl have the power to die." (3..5. 239-242)