I have never seen a calcium deposit or a fat deposit that looked like that. Try to get a friend to take some pictures of her from the side, and close up of the blister. Is her cage humid,.. like all over, does she spend a long time in her humid hide. She doesn't look skinny to me, she could very well be prego, I had pics of my girl up and everyone said "she's not gravid" about six eggs later, I decided to take a different opinion. If there is water behind the blister, like the type you would get from hard work, I would really take her to a more qualified vet, cause a reptile vet shouldn't give you a "i don't know" diagnosis. If they don't know they should have taken a sample of the fluid (probably less painful than you'd think). So that being said, good luck with the eggs, and really I would take her somewhere else, (do at least move her into another room away from your other scaley buddies). 


