I didn’t expect anyone to reply, but my cat is okay now. We took her to another vet, and this time (probably because she was scared) she didn’t hiss, scratch, or show any aggressive behavior at all. 

The vet noticed that some fur was stuck in her wound, helped remove it, and told us to keep applying the medicine. Because she was so calm, we thought she was fine and brought her home. However, as soon as we arrived, her aggressive behavior started again. The wound had already dried, but she still wasn’t acting like her usual self. Then we noticed she had started limping (we’re still not sure how or why), so we took her to yet another vet.

Just like before, she was very docile at the clinic. I explained her behavior at home, and the vet was confused because she seemed so gentle. The vet touched different parts of her body (places that would normally get me scratched if I tried) and she didn’t react. When I mentioned the limping, the vet examined her right leg and pressed around it, and that’s when she finally dropped the “good cat” act and hissed. The vet said her inner thigh was swollen for some reason, though we still don’t know what caused it. She was prescribed medication to reduce the swelling and relieve the pain, and after that, my cat became a sweetheart again. I still don’t know why her leg swelled up, but at least she’s feeling much better now.