Awe, the poor thing, it's definitely Mouth Rot, and a bad case of it, which is not your fault, that vet didn't know what they were talking about. This will only get better by taking cultures of her mouth and sending them off to determine what type of microbe is causing the infection, and getting her on the proper Antibiotic/Antifungal, both orally and probably by injection and then also a topical application in and around her mouth. You need to find an experienced Reptile Vet/Specialist to treat this, as it's extremely serious, and yes, she's in a great deal of pain and need some pain medication as well, because it's inevitable that she will stop eating soon...
If you need help finding a proper, experienced Reptile Specialist, please just let us know where you live and we can find the closes one for you, but please don't wait any longer to get her in, I'd even call them and tell them it's an emergency, and explain how the first vet was not a reptile vet and misdiagnosed "Mouth Rot", and now she's very much worse than she was, and needs to have cultures done immediately. If it isn't treated properly soon, the infection is going to spread to her bloodstream and cause sepsis, which is fatal. Mouth infections can also spread to the heart and caused Endocarditis, which is an infection in the heart, which is also fatal. So this is very urgent.