Evicting a roommate who feels she cant be evicted?

Immediately give her notice. You can give her 60 days if you can stand her that long! Have it in writing. You may end up in Court, so make sure you document times and dates when you talk to her about leaving. I would be very serious about having her clean up her mess pronto and keeping it that way until she leaves. Putting on pressure will speed her into finding another place to live. If she wants to be a mess, she can do it elsewhere. You have been so generous - no one can say a word about your patience in this situation.