I've searched bing for the largest images of stormy daniels.
I did it for science.
What stood out the most is how she positions her body or clothing in a way to obfuscate this part of her body. She either has her leg positioned to block this part of her body, or she is wearing something around her midriff.
Imagine you had a big scar near your appendix and had to pose nude in a way that would hide it, in case your camera guy didn't have good photo shop skills to air brush them out. How would you pose? You'd pose like stormy.
Links to source files:
https://www.imageweb.ws/media/images_640/12/stormy-daniels/stormy-daniels-1383316.jpg
https://www.lemmecheck.xxx/wp-content/uploads/2015/04/wicked-stormy-daniels-41591-07.jpg
The NXIVM brand is located to the left of the 12 on the clock tattoo, about 4-5 inches, or a hand width.
I'd say that's definitely a scar. Confirmed using two different photos of her.