Oh, that's not right at all...her lower jaw IS swollen. She needs vet care, might be an abscess or some other infection. Was she being fed live rodents? (if you don't know, ask previous owner)
She might have gotten bit in/on her mouth from a live rodent- don't wait too long to call a vet, most can't see you right away, & you can always cancel appt'mt if she somehow improves. But most (like this) get worse,
& since you didn't notice this when you first got her, I'd assume it's getting worse pretty fast. Make sure you see a herp-qualified vet:
http://arav.site-ym.com/search/custom.asp?id=3661