It looks like scale rot to me..but I could be wrong. Either way I'd get to a vet asap and not wait for it to shed.. Until then get some betadine(an excellent antiseptic) and apply that 2x a day also... The way I did it when my BP had a minor case of scale rot was to apply it with a Q-tip along the affected area, then wait 15-20 minutes and then soak her for about 15-20 minutes in warm water(kind of to wash her all off) and then take her out, dry her off and apply neosporin. Also if you havnt already, switch her substrate to papertowels or unprinted newspaper. Also describe for us how you have your heat set up, and pictures also help.