Florida - Last month rent - Tenant trying to use security deposit

[Steven Segal]

Looking for how people handle this in Florida....

Tenant is moving out due to an increase in rent. They said that they want to use security deposit to cover last months rent, but we obviously do not allow that.  She said she has no option due to amount of money she will have to put down for a new place and moving expenses. However, this is obviously not good for us. 

How do you generally handle this situation? Do you evict (seems like money you may never get back, ect)?