get that hole you can see muscle fibers at checked out first and foremost a huge wound like that needs cleaned or infection will set in
but that other stuff from how it sounds could be caused by being constantly being stressed. stressed animals get sick easier and to much stress can kill a snake (maybe not directly but very stressed sometimes refuse to eat) like you say this girl you can literally see where her prey has chewed on her to the point you can see muscle fibers (should of had them arrested for animal cruality) could of got charged for either watching the rat chew on the snake that long or for not taking it to the vet to get it proper medical treatment either way my local animal control would of taken the snake from them if they would of seen it in that kind of conditions being allowed to sit around with very visibly wrong stuff going on with the snake (think i would of punched them if i would of seen that)
when you take it to the vet tell the vet there name cause I'm sure any other pets they got are more then likely treated about the same.
just let her be for at least a few weeks guaranteed she was stressed to the max.
you will be surprised how quick that wound on her back will heal once it gets proper medical attention. i had a wild caught from back when they use to burn fields and caught all that come out alive (ones with huge burn scars) i had one that had a 4 inch long burn mark after a year you could only see the outline of the burn had pattern just a Lil faded looking from the rest after 2 years the outline was barely visible and couldn't tell a difference in color. if rember right shortly after 2 whole years i trader her off to a buddy who hatched some burm eggs for 2 babies