To what extent is Cathy Ames a stereotypical female character in East of Eden?
You might find it helpful to start off by thinking of what you mean by a stereotypical female character. Normally we use this phase to think of a mother-type figure who is warm, sensitive, caring and loving and above all nurturing.
If this is your idea of a stereotypical female figure, then it is clear that Cathy Ames is nothing like this whatsoever. She is described as a monster by the narrator, and does not "nurture" so much as destroy, manipulate and oppress. She appears to be the opposite of a stereotypical female figure in the way that she is presented in the text as not having any decent feelings.
If we just have a very quick think through her catalogue of crimes, she makes her Latin teacher commit suicide. She murders her parents through burning her home. She becomes a prostitute and then runs one such establishment, using techniques such as blackmail in order to extort money from her clients. Even though it appears that she softens somewhat towards the end of her life, it is clear that she is definitely not your stereotypical female figure.