Hi,
Do the folds go along her body or from top to bottom?
Do you have a picture of her?
Has she ever eaten?
And, I have to ask, what on earth would make you select non-eating small snakes from a communal tank?
It just seems to be setting yourself up for problems.
Can you run through the temps at the respective hot and cool ends of the split tank and how, and where, you are measuring them? A picture of the setup might give us something else we could suggest as well.
dr del