It is a tough situation. Antibiotics are for bacterial infections so unless the abscess is a secondary diagnosis to a bacterial infection, the antibiotics won't make it go away. On the other hand, if she reacts to anesthesia, putting her under to pull the tooth would be a problem. I would suggest further discussion with your vet so that fully understand the risks and benefits of both courses of action.
We have just had to have our cat Sooty to the vets for the same problem, she is 15 years old, she was in pain and her face was puffed up, she is now fine,the only drawback is she will not talk to either me or my husband, and looks at us as if it was all our fault.
I hope both kitties are doing better by now, were they able to safely have the extractions?