I suggest to take a really good look at her and make sure she doesn't have any little friends on her(mites), not saying for sure that's what it is but defiantly worth a check. Best of luck!
Thats the first thing i thought at first. But i got her from a very reputable breeder and i checked her myself. No mites.
Reputable breeder or not it can still have a case of mites. mites are not always seen by the naked eye until they grow to and adult size which is often too late. Check temps , that could also be a reason for soaking but I believe you have experience in snake keeping so my money is on that it has mites!