It sounds like you have your hands full!
I agree with everyone else that you should consider switching her food and until she gets the point of the potty pad, maybe you should cover the entire bottom of the playpen with the potty pads and duct tape them down. It will be a lot easier to clean up! Reward her when she does her business on the potty pad (which will be easy because the whole bottom of the play pen is a potty pad). And then gradually make the potty pad area smaller and smaller, rewarding her each time she does potty on the pad. Hopefully she will get the point!