You're right, she does know a great deal about mega evolutions, so one of her Pokemon could be holding a mega stone.
What someone pointed out to me from the mugshot was that unlike the other battle mugshots with the different gym leaders, hers seemed like an ordinary one, much like when you battle that Lass from an earlier screenshot. This could mean she might battle us before the actual gym battle with just two Pokemon. Either way I'm kind of over it now, I am just hoping she doesn't turn out to be another Chuck-like gym leader who goes by too quickly.