Spirit River Nami skin causing fps drop on new map

I've luckily haven't had any performance problems with the new map. It works equally well if not better than the old summoner's rift on my computer. The one exception I've noticed is if I happen to be in a game with a Nami with River Spirit skin. Then the fps of the game fluctuates wildly and never remains the stable 60fps as it does in all my other matches.