I hope you find her. I would go back and recheck everyplace you have already checked. Try spreading some flower on the floor next to the walls. That way if she crawls through it you will know. I would get a box cut a small hole in it (one she will just fit into) get one of those live trap mouse traps and put the mouse in it and put it in the box. Good luck finding her and don't loose hope, sometimes they can be gone for a long time and just suddenly show up.