Actually, you could turn her into the health dept and NOT move out. Nothing she can do about it if you have a year's lease. Health dept will make her get rid of the mice. If you need to leave the premises....you can go to a hotel until it's safe to go back in. (wouldn't think that would be more than 24 hrs)
I spent 20 yrs renting. What she's telling you is that if you don't like it, MOVE. She's not planning to do a darn thing. She's expecting you to either back down, or move out.
If it were me, I wouldn't move. Not when I'd just gotten moved in and when there is no where available that you can afford. Instead I'd call the health dept and turn her in. She will get a hefty fine if she doesn't comply and correct the situation. If she doesn't........Do it again.
I have a strong dislike for slumlords. And I don't put up with their carp, either. With one, I contacted a lawyer for consult and found out what to do to get the fastest results. (alot of lawyers will give you a half hour with no charge) Our hot water heater had ruptured and leaked all over the carpet......By the time the landlord got around to doing something about it, the carpet was meldewed and reeked. In the end, I got new carpeting.
Sometimes you have to be both a *itch and stubborn. I'm both when I want to be.
Hugs