Tenant breaking lease HELP!

[Mandy Alexander]

Our tenants signed an 18 month lease. One year into that lease (12/11/15) they gave 30 day notice that they would be breaking their lease in order to buy a home. They acknowledged the lease buyout fee of 1 1/2 monthly rent and Jan's prorated rent till the 11th and had no problem paying that initially. They chose to move out sometime before Xmas and we received the keys and did walk thru on 1/1/16. I am a real estate agent and immediately put the house on the Market. I asked the tenant on 1/1/16 if she would still like me to give her 24 hr notice even tho she no longer occupies the home. She said no. I had a showing that day and the next and even held an open house for about an hour the following day. She happened to drive by and is now angry that we had an open house. She was supposed to pay her pro rated Jan rent today (tho it was due the 1st but with the holiday I let it slide.) The day is over and there is no rent or lease buy out fee in my acct. (She always does direct deposit). Here are my questions:

1. Did I do anything wrong? My belief is that she relinquished her interest in the home when she handed the keys over. She literally couldn't get in if she wanted to. There is no damage to her. I have a right to attempt to sell or rent it out. She also gave me written permission to waive the 24 hr notice. Am I wrong or is this lady crazy?

2. When is the lease buy out fee due? Would it be when the last rent payment is due or on the last day of her 20 day notice which is 1/11/15. The lease doesn't specify.

3. What is my next step? Rent is late as of 11:59 tonight. I don't even have this lady's forwarding address yet. Do I email her a stern letter/notice? Start out nicer? HELP! This woman is a paralegal and is just waiting for me to screw up.....