Guys, how strong should I remain on my position for her to move out?

I've told her she has some time to find a place, but didn't specify by which date she needed to be out.

I think the longer she stays home the more she'll eat cake. I do think moving out will be a rude awakening for her, but I mainly want her to move out because of the betrayal which she still doesn't admit to - or is her being in the spare bedroom ok?