Hi, and welcome to Pet Talk!

I don't know from your post if there is a litter box in there or not? If not, well, I know the answer to the question. If so, is it ALWAYS in there? If not, well, I know the answer to the question.

Cats need/like consistency. Make sure there is a litter box in there, all the time, and that she has acess to it all the time.

Also, she may be peeing the bed in reaction to putting her in there. So, maybe you shouldn't put her in there? Why does she have to be put in there?