Would Juliet be more likely to share secrets and ask favors of her mother or her nurse?
Given the fact that Juliet tells the Nurse about Romeo, it's obvious that she confides more in the Nurse than in her mother. It is the Nurse that Juliet sends to find Romeo the morning after they met in order to learn the partriculars about the young lovers' marriage plans. The Nurse is the one who brings the rope ladder from Romeo so that he may sneak into Juliet's room to celebrate their wedding night. When Lord and Lady Capulet announce that Juliet is to marry Paris, Juliet still does not confess to her own mother that she is already married to a Montague. Instead, she goes to the Friar who concocts an elaborate scheme to fake Juliet's death. It is only when the Nurse tells Juliet to forget about Romeo and marry Paris instead that Juliet ceases to think of her as a friend and confidant. That is why the Nurse is not in one the fake death scheme. Up to that point, it is clear that Juliet trusts the Nurse much more than her own mother.