Like many other mothers of teens, Lady Capulet and her daughter clearly have a troubled relationship. The interactions between Lady Capulet and Juliet are strained and distant. Lady Capulet does make an effort to reach out to her daughter now that she's of an age to be married. But it's obvious that Juliet's closest bond is with the Nurse; Lady Capulet never even comes close to challenging that.
As a result, Lady Capulet doesn't come across as a particularly great mom. The big question with her character is why. Why isn't she close to her daughter? Why isn't she supportive when Juliet needs her most? Just when Juliet needs her mom's support, Lady Capulet coldly ignore her daughter's pleas to help her avoid marrying Paris. After Lord Capulet storms out, Juliet turns to her mother to soften her father's punishment. Juliet begs her even to delay the marriage. Lady Capulet responds, "Talk not to me, for I'll not say a word / Do as thou wilt, for I have done with thee" (3.5.15). That's pretty cold. What's up with that?
There could be a few different things going on here. It seems very likely that Lady Capulet herself had an arranged marriage with Juliet's father, and it seems she went along with it obediently. When Juliet rebels against the planned marriage with Paris, she is rebelling against her mother's way of life, and against the kind of marriage that Lady Capulet learned to suffer through. If Lord Capulet is an abusive husband, that gives Lady Capulet further reason to refuse to defy his wishes, even for the sake of her daughter. Also, in Shakespeare's day, women were expected to be "obedient" to their husbands. We should also mention that some rather edgy modern interpretations of the play go so far as to say that Lady Capulet is having an affair; or at least actively pursuing one. We're guessing these productions of the play are picking up on Lady Capulet's over-the-top praise of Paris's manly virtues (1.3.9) and her excessive grief over Tybalt's death (3.5.7).