Dear if something happens?
I appreciate your concern, and you know your sister better than I do. The relationship between you and your sister, as landlord and tenant, ended as a "matter of law" upon the issuance of the warrant of eviction to the Sheriff. You could follow through on the eviction, allow for the changing of the entry door locks, and that should legally fully protect you, as the execution of the warrant of eviction, is the process where legal possession is transferred back to the landlord.
You could also prepare a receipt for your sister regarding the keys she turned over with her admission that the surrender was voluntary in light of the pending eviction, and that she holds you harmless.
If you go that way, I would recommend that you have your attorney make sure you are protected as well as you would be by the Sheriff executing the warrant of eviction.
The answer provided to you is in the nature of general information. The general proposition being that you should try to avoid a bad outcome if you can.