My daughter tore some of my bathroom wallpaper off too a couple of years ago,so I can really relate. It is very frustrating. We had to wait awhile to fix it too because of finances. But I do have to say if I were in your shoes,I wouln't ask the parents for help to fix it financially or otherwise,becouse the little girl was in your care when this happened,and I would think that makes you responsible. Your the babysitter. I would just chalk it up as an expensive lesson learned. I too used to babysit and while I was changing a diaper and feeding a newborn,another child found some house paint from our remodeling and decided to paint the babybed and all over the walls in the kids room where I thought they were watching barney.I got most of it off,but did wind up repainting.that room.lol.
I didnt say anything to her parents becouse I didnt want to look like I wasint doing my job right Ps. This was not meant to sound rude at all. I hope you dont take it that way. Good luck in whatever you decide with this situation. I hope all goes well.