As far as the story goes I'd say bigger is better (much as Vanessa has been thinking all her life
). Vanessa is a good character and possibly your best, but I think Katherine can still give her a run for her money. That said Katherine's story is over (at least for now - I don't know your plans for that) while Vanessa still has unlimited potential!
By the way, are these characters you write based at all on people you know or are they pure fantasy?