That looks like a possible burn on her back. Can't tell from photos for sure, but also looks like something may be going on along her spine.
Burns are usually caused by a badly designed thermal gradient within the enclosure- the background temp may be too cool for the heat light, encouraging the lizard to stay too long under the lamp trying heat it's core, meanwhile burning the surface. They use core temperature for thermoregulatory behavior, not surface, so it can be easy to burn the skin.
The solution is to either provide a more gradual temperature gradient in the enclosure (rather than a "hot spot" within a cool enclosure), and/or a cooler basking area (by raising the lamp off the cage or lowering the wattage of the bulb).