They've threatened to take the locks off using a locksmith if I don't give them a key.

Just coming back to update all those that offered advice on this original post....I did go down the eviction path, won the eviction hearing and, as of today, have regained possession of the property, to include having a locksmith rekey the locks.

I currently manage about 200 reo properties and theres lots of maintenance from rekeys, trashouts, winterization, and repairs.

If you are dealing with an out of state owner have them sign and notarize a 'Locksmith agreement" have the locksmith come out and let you into the home once you have received the paperwork.

There is one precaution to take before your rekey the whole house, PM me for more info.Best.

If you needed a locksmith to unlock your car on the weekend, he would probably take maybe 5 mins. to do that, once he arrived. 

Inexpensive and can rekey them yourself - takes about 20 seconds per lock to rekey.

I used to work in Multi Family for a long time, and any time I ever had to fire my maintenance super (he had a free apartment), we usually had to evict if they did not vacate within thirty days after we had terminated his or her position.2nd, Change ALL of the locks immediately after you let him go, never risk the chance that he has keys or gave keys to someone else, you could be setting yourself up for a liability issues, and that will be a lot more than re-keying some locks

Let them do the simple stuff, paint, carpet, rekey.  

If she refuses, hire a locksmith and bill her (warn her first).