First of all, Lady Capulet is Juliet's mother. A mother is suppose to be close to her daughter, and is the person who knows and understands Juliet the most. But in this case her mother is the first person to let her down. For example, when Lord Capulet made the decision in act three scene 5 that Juliet should marry Paris, her mother stood up for that decision even though she knew that Juliet didn't want to marry Paris. I think her mother should of been on Juliet's side, because she's her mother and she has experience in marriage and should know marrying someone you do not like is not a good idea. Also, another betrayal by Lady Capulet is that she teaches Juliet to judge men by their money, their social rank and their appearance. For example, she recommended Paris to Juliet because he is rich, good looking and on the Capulet's side. This is not good. Because Juliet really does love Romeo, and when her mother says things like that, it really makes Juliet upset, because Romeo is not rich, and their family hates her family and vice versa. These points show how shallow Lady Capulet's character is. This prevents Juliet to ask advise from her mother, and cannot get guidance from her.
Secondly, Friar Lawrence is the second person who betrays and lets-down Juliet. As you already