Well, I agree with others. Try contain her on one part of the room. Eventually, she'll be pooping there *try to use better words but my english sucks! >_<*

Or try to put her in a cage, if she like it. I have aunt who keep her persians inside a cage and feed them there. There's a litter tray there IIRC.
Hope I help.

Edit: Ah, Animalia already suggest the pen/ cage stuff. Guess I should've read it better.