I am a landlord in Tennessee, What kind off letter to I give notice to a I CollegeTenant after 2 months of a year lease gave me verbal notice she was moving out due to a family illness. She moved out and paid that months rent and returned keys in the deposit box. In the lease it says tenant is liable for a re-rental fee of $200.00
And if no replacement is found for the lease all fees and payments are due under the term of the lease.

It is not a legal termination of a lease to just give notice. That lease is in effect and you should start by billing her the $200 and also stated that you will find a new tenant as quick as possible but until that happens she should keep paying the monthluy rent. When and if she defaults you can sue her. You may win but collecting on a judgement can be dicey.