Are disney princesses as simple as they seem?

While some Disney princesses are portrayed in what would seem a completely sexist way, others do have glimmers of independence. Belle, despite her beauty being the reason The Beast does not kill her, is an avid reader and is quite intelligent. In her first meeting with the beast in which he invites her for dinner she stands her ground and refuses to go (though some people may say this is typical of a woman to sulk when she doesn't get her way, however she could be standing her ground.) Jasmine also fights back against her fathers wishes for her to have an arranged marriage. 

Aside from these two, the other Princesses are still very trivial and one dimensional, relying on their beauty and maternal instincts in order to save themselves and their lovers. 

An interesting point is always raised about the whereabouts of each of the princesses mothers. Why do they all come from broken families? Is the mother always vacant to highlight how a loss of motherly love affects the family? Or is it that mothers do not play an important role in a girls life and that daughters are more likely to rebel against fathers?