Wanting to get grandaughter out of unfit parents home?

My granddaughter is currently living with her mother and step-father. She has a very rare health disorder that causes her not to be able to go to school, so she does it online. She got in trouble a lot during her first year of high school by getting behind in her school work often which was mostly caused by her health and her mother needing her to go help her clean houses (her mothers buisness) during the day and now her mother makes her go with her during the day every day and forces my grandaughter to do her school work at late hours (sometimes even after 7 at night). She also verbally abuses her by calling her a fat cow (my grandaughter weighs barely over 100 pounds at 16 years old), a *****, a worthless daughter and a dissappointment (because she cant get her school work done on time most of the time). They have also intentionally hurt her and smacked her a few times over the years. My grandaughter if never allowed out with friends or to family houses. She has a boyfriend who she spends maybe 6 hours a month with. She cries all the time and is very depressed. Her father is a alcholic and not the best place for her to go. We all love her very much and want to get her out of that enviroment. I am more than willing to take her in, we have a extra bedroom and the means to take care of her but, we are worried because my daughter has said more than once that if my grandaughter ever called social services or tried to leave she would beat her till she couldnt walk. I want her to be safe but im worried about her so much. Is there anything I can do?