After deworming my cat how long until her "pot belly" goes away?

It's a long story but my husband brought home a stray cat. It is a very nice cat who he has had a lot of contact with because he is the police officer of our small town. He took her in because people were complaining and he thought she was pregnant. We already have 3 cats. So before he brought her home he took her to the town Vet Clinic and she was given her shots/dewormer/flea medicine and a look over. The Vet said she was probably pregnant and if so about 4 weeks along. He said he couldn't be for sure though without doing a sonogram. My husband didn't want to pay for that as well since all this was coming from our pockets. We've had her for 2 months now and she never had any kittens. We talked to the Vet and he said she probably absorbed them because it's a bad time of year for her to be pregnant. Well the other day when I was scooping the boxes I saw in her stool a worm or something. The vet said it was probably a tapeworm and gave us Profender for all 4 cats.

My question is~ her belly is still huge, how long will it be like that until it goes to a normal size??? I am guessing that she was never pregnant but she had worms... that's my guess. I just want her to be healthy, I feel so bad for her.

Anyone with any experience?