Thanks for your replies everyone.

I agree, Lizzie, I wouldn't want to medicate the cat for something she may not have. It could cause even more problems for her.

What I think I'm going to do is, give her the meds the doc gave her for the allergy. She also gave her meds because, although the mouth infection cleared, her mouth is still a bit swollen. Once she finishes these meds, I'll see how she fares.

I'll keep looking for evidence of worms in all the cats. If anything shows up, I'll take them to the vet for the pills.

Thanks again, everyone!