The Nurse has been with Juliet since Juliet was an infant. She nursed her, named the day of her weaning, lost her own daughter Susan around the same time. She is the closest thing Juliet has to a mother in any practical sense — the one who knows her birthday, her body, her appetites, her temper. She is also bawdy, tireless, opinionated, and a little vain. Shakespeare gives her some of the most loveable comic writing in the play.
What the Nurse wants is for Juliet to be married to a good-looking, well-funded young man and to be allowed to be happy about it. She wants to be the one Juliet whispers to. When Juliet falls for Romeo, the Nurse, after a bit of teasing, makes herself the lovers’ courier. She runs back and forth between them through Act 2 because she wants this to work.
She doesn’t change, exactly — but the play lets her down with a thump. When Capulet threatens to disown Juliet for refusing Paris, the Nurse, terrified, tells Juliet to forget Romeo and marry Paris. “He’s a lovely gentleman,” she says, more or less, “and Romeo’s gone.” It’s the moment Juliet realises she’s alone. The Nurse is never on Juliet’s side again the way she was. Shakespeare shows you, kindly, what an honest, ordinary love that’s not quite enough actually looks like.