I don't know what could cause that, but I think you're right and should get her back to the vet right away. Is your vet a reptiles specialist? Could it be an enlarged organ like the kidney? Be careful, antibiotics like Baytril can be harsh on the kidneys. He might have to take an X-ray to find out.
I got the following info from Melissa Kaplan's site ...
"When kidney failure occurs, its external signs--what you see--happens suddenly and the animal usually dies soon thereafter. Signs include anorexia, weight loss despite eating, lethargy, swollen or distended abdomen, frequent drinking or voiding, grossly swollen neck. Upon x-rays, kidneys, not normally visible due to their position in the pelvic area, may be seen protruding up into the coelomic cavity; they may also be felt."
The entire article is at:
http://www.anapsid.org/iguana/kidneyfailure.html
I know it's about iguana, but most of the info on her site pertains to most reptiles. I'd get her checked out asap! I don't mean to alarm you, but a swollen abdomen is nothing to mess with. And keep her hydrated. Soaking won't always be good enough unless she's drinking the water. And try the baby food.
Good luck and please keep us posted on her situation.
Veronica
-----

Beautiful Dragons