Have you considered taking her back to the vet to make sure she is doing well. My niece had her cat spayed and she seemed to be fine for a few weeks, and then unexpectedly passed on from an infection that they weren't even aware of she had. her personality had changed somewhat but everyone thought it was from her surgery healing. I do hope that they become friends again. I have 7 cats and not all of them were overly friendly after their surgeries. I would have her checked at the vet.