Some snakes just hate people, plain and simple. There is no complex reasoning, they just hate people lol. Live with it or re home them. But yes, first off you need to get the whole parasite issues and husbandry issues straightened out. Then you can see if you can work with her.
And no matter how 'tame' a snake is, they can still bite. Like i said, i got Rosey when she was an 18 inch worm over 5 years ago and she has never hissed or bit. She didnt even hiss or bite when the vet shoved a needle in the lump on her nose to take a sample of the liquid to find the best antibiotic for her. But she tagged me when i startled her and about a minute later, i reached in and just scooped her out and she was fine. Stuff happens.
But again, get the snake feeling better and secure, then worry about making friends with it. Heck I've had my GTP almost 3 months now and never handled him/her. I just let it settle in, get eating good and pooping. Now it is curious as can be and cruises all over at night and even checks me out when i clean the cage and stuff. And it even peeked it's head outside the cage door when i was standing there to just see what was outside and look at me. Once a snake feels comfortable, they will become inquisitive which is when you can start working with them as it will be on their terms and not yours. They arent a dog, you arent going to 'break' them into being submissive.