Hi and welcome. I’m afraid that looks like a thermal burn. How close can she get to her basking light? What are your temps? Little ones like to screen walk along the top upside down, which is another way they can get burned, so making sure your basking temp is no higher than 80F and raising the lights at least a few inches off the screen is the best way to prevent that. Keeping the distance between lights and highest branches at least 8-9” is another way. That is a large part of her little body, so it’s pretty important she is seen by a good vet and get treatment. If you post some pics of your enclosure, we can maybe see some other things needing improvement.