During Act III, scene iii, the Nurse visits Romeo in Friar Laurence's cell. She is disgusted by his reaction to his banishment, and it may be this display of emotion which turns her heart against him. Then, in scene v, the Capulets inform Juliet of her impending marriage to Paris. Now, as audience members, we already know Juliet is married to Romeo. The Nurse knows this as well. Yet Juliet's parents remain blissfully unaware of the situation.
It is the Nurse's advice to Juliet that turns Juliet against her. When Juliet, heartbroken & weeping, turns to her for help, the Nurse suggests that she marry Paris and forget Romeo:
I think it best you married with the County.
O, he's a lovely gentleman!
Romeo's a dishclout to him. An eagle, madam,
Hath not so green, so quick, so fair an eye
As Paris hath. Beshrew my very heart,
I think you are happy in this second match,
For it excels your first; or if it did not,
Your first is dead—or 'twere as good he were
As living here and you no use of him.
This is the breaking point for Juliet. She has lost all confidence in the Nurse, and will now rely only on Friar Laurence for advice, and herself for action. It is this moment that reveals Juliet's independence and inner strength. she is no longer the obedient daughter, but a willing participant in her own fate.
Nurse, for once, in these scenes gives Juliet some sound advice that Juliet does not want to hear. Following Tybalt's death and Romeo's banishment, the nurse becomes even more deeply entangled in the lovers' plot. When she returns to the Capulet house after telling Romeo to "snap out" of his misery, she discovers that the Capulets want Juliet to marry Paris. Nurse realizes that she has gotten herself into some trouble and starts to advise Juliet to listen to her parents; she also tries to point out some of Juliet's "flaws." Juliet, of course, does not want to hear Nurse's advice or have to continue listening to her babbling and overworked emotions.
After Romeo is banished and Juliet's parents tell her to marry Count Paris, Juliet asks nurse what to do. Nurse replies saying Romeo is gone marry Count Paris. Juliet hates this because she loves Romeo and they are married. She is staying loyal to Romeo.