Early in the play, the answer is the Nurse. Juliet was born when her mother was quite young, and was turned over to the Nurse who breastfed Juliet, and basically raised her as her own daughter. The Nurse is a mother to Juliet. She has had little communication with her real mother. Shakespeare shows us this in Act 1 by having Mrs. Capulet send the Nurse away so she can talk privately to Juliet and then call her back in a panic when she realizes that she has no idea how to talk to Juliet. As a result, it is the Nurse Juliet trusts, not her mother.Later in the play, Juliet will not trust either of them.