You've only posted that one photo of her tail-end, but I'll be honest, I've never seen a BP in such poor condition. I want you to be aware of how important it is to get her to eat. Even if it's a live fuzzy mouse. And again, don't try to feed too much right now...if it leaves a "bump" in her mid-section, she will likely have trouble digesting it.
It's not about "filling her up"...it's all about not overwhelming her digestive system at this time. When a snake is starving, they may not have adequate digestive enzymes available for larger prey. I'm telling you this with about 35 years of keeping & rescuing snakes...I've been very concerned ever since you posted that one photo of her.
She needs "slow & steady" regular small meals to regain her body weight. She's way too skinny- her body resembles a colubrid more than a BP. I'm sorry to be the one to tell you this, but I hope you can get her healthy.
Remember, wait until evening to offer food.