Tenants wants out of lease in 15 days

[Luke H.]

A tenant just called me and asked if I could work with them on the following.  They found another property and want to be out of mine by Dec 15th.  They even asked if on tomorrow, Dec 1st she could prorate the rent.  I told them I would have to grab the file and take a look at the lease before agreeing to anything.  I also told them they are still responsible for the entire rent payment on tomorrow..

1) The lease states that the tenant must give 30 day written notice BEFORE the anniversary date.  If they do not give 30 day written notice the lease automatically renews on the anniversary date.  

2) The anniversary date is tomorrow Dec 1st.  At which time the lease automatically renews for an entire year.

3)They said she just sent the written notice and I haven't gotten it.

So a few hours before the lease is set to automatically renew for the entire year I get a call and in what I consider to be an emergency voice tone I am asked if I will let them out of the lease. 

This will have a major impact on my schedule, routine, revenue, and labor force.

Suggestions/ Feedback/ Thoughts on how to proceed here.
Thanks