As @Starryk says, it is difficult to define what best performer means. It could mean so many things.
In a general sense, it could mean the most consistent performer, the most enthusiastic performance, or the most entetaining on a general level. In this case, my view would be more objective in that I may pick girls who I don't necessarily regard as my favourites.
On this basis I would say that Melissa, PussyKat, Alizee, Pepito, Dorothy Banks and Jana Cova come under the best performances in that I think they are consistently good over all their cards.
But if I were to girls whose performances suit my specific taste or where I really like their performance in one specific card then the list is slightly different:
Alizee, Jenni Gregg, Kristine Kristalis, Chems, Jana H and Britney come under this category.
Without seeing many of her cards, I think Suzie Q is definately the best pole dancer, and thus the best performaer in that category.
So on the basis that Alizee is the only firl in both the lists I gave and is not bad on the pole compared to some of the other girls, it would have to be Alizee.