Final answer:
Juliet doesn't trust the nurse anymore because the nurse prioritizes her own benefits and a good position over the well-being of her own child.
Step-by-step explanation:
The reason why Juliet doesn't trust the nurse anymore is because the nurse betrays her trust by suggesting that she forget about her own child. In Act I, Scene 5, Juliet asks the nurse how she could have the heart to put her own child out among strangers. The nurse replies that a poor girl who has gotten into trouble should be glad to and that the wicked man didn't do a single thing for her. This response shows that the nurse prioritizes her own benefits and a good position over the well-being of her own child, leading Juliet to lose trust in her.