Yeah, in the novel, she is inspired by Joan of Arc and has visions and all she talks about is being "My Lady the King's Mother" and "I shall sign myself Margaret R: Margaret Regina!" constantly. Oh, and whining. About. Everything. I don't think they have captured a lot of Margaret's wiliness nor her intelligence, mostly overdoing the piety.
I know a lot of people who still believe things like that about Richard. I don't have a side in this one, which is funny, because I usually do in historical arguments. York vs Lancaster, meh, whatever!