What does juliet mean? . . o most wicked fiend! is it more sin to wish me thus forsworn, or to dispraise my lord with that same tongue which she hath raised him with above compare so many thousand times? go, counsellor; thou and my bosom henceforth shall be twain. i'll to the friar, to know his remedy: if all else fail, myself have power to die (iii. v. 252-259)?

Juliet is saying that her nurse wants her to go ahead and break her vows. The situation is confusing to her because the nurse is now saying bad things about Romeo after she has said so many good things about him. It is almost like she was encouraging her and now is discouraging her from being with him. She has decided that is best to no longer tell her secrets to the nurse. She is heading to go to the friar in order to get a potion that will kill her, if they cannot come up with a better solution.