Tenant leaves but does not return keys
I rented an in-law apart to an attorney with a 1 yr lease that expires 8/31/08. On 7/15, she called me & said she had rented another apart and she would move out in early Aug. I told her I would post an ad on 7/20 when my out of town guest left. On her own she posted the apart for rent and found someone who was interested in the apart & could move in as soon as she left. I posted the listing on 7/20, & the first call I received was from a previous tenant who had moved back to the area. She requested 2 days to make a decision.I met with the person my tenant had found but told her my previous tenant was my first choice. She did not fill out the rental app.I agreed to rent to my former tenant & she had to give 30 days notice. Through emails my current tenant told me she would be moving her stuff out on 8/4, and she'd be back to clean on 8/9. She everything, left nothing in the apt but did not give me back the keys & is not responding to email or phone. She is upset because I am requiring her to pay rent until my new tenant moves in on 8/23. She did pay pro-rated rent through 8/19. Can I change the locks & charge her for this if she does not return the keys? Is she still liable for her portion of utilities until she returns the keys?