Maybe somebody's done something like this already, but: a fight between two evil young women from Oscar-winning movies who are out to destroy and supplant the middle-aged divas who love them: Eve Harrington (Anne Baxter) from All About Eve vs. Veda Pierce (Ann Blyth) from Mildred Pierce. Who wins this battle of the anti-ingénues?
Advantages for Eve: She's smarter than Veda, better able to manipulate people to get what she wants, better at strategy. Advantages for Veda: She's more evil, more violent, and hotter (I don't know how that will help her in a fight, exactly, but it can't hurt).
(This is confined to the movie versions, so Veda from the original novel doesn't apply here.)