Hey Bryce,
April has pretty much said it. It looks like an old layer of skin is still attached to your boa, which makes sense given that you said she is in shed, and the old layer of skin appears to have dried out.
I have a little male possible jungle that arrived very thin, and absolutely refused to shed on his own. He used to look very similar while in the late stages of his shed cycles. I sprayed his enclosure with water, keeping the humidity up around 50% while he was in shed. He still wouldn't shed on his own. The skin sat on him until it started bubbling and cracking and falling off in some places, and he still wouldn't shed. I carefully assisted him with each shed once the skin began to bubble and crack, using water and very gentle and slow rubbing. I'm not certain why he did that. He FINALLY shed on his own just a few days ago, after refusing to do so for several months.
In all honesty, I'm not sure what did the trick. I didn't change anything. I kept him on a regular feeding regimen, and he's gained a lot of muscle from that. He still has some evidence of his spine along the upper 1/3 of his body, and his ribs are still somewhat visible, but mostly he's nice and square now. I still maintain humidity around the same level I did before, increasing a little by misting whenever he goes into shed. It's possible that his refusal to shed was related to his physical condition, but I can't say for certain. All I can say is that he looks healthier now, and has finally begun to shed on his own.
I wish I could help more than that. All I can really say is what I observed and tried with my own little guy when he appeared to have a similar issue. I would give the same advice April did. Perhaps try increasing the humidity a bit, make sure there’s a water dish large enough for her to curl up in if she wants a nice soak, and be patient.
Rubbing the skin off for her can be a bad idea, so definitely try to let her do it herself. I’ve never had to do that with any other boas before. I’m not advocating that as a solution, only mentioning it as a potential last resort. If you do end up deciding that it is necessary, be very slow and gentle.
Best of luck.