Is there a way I can get custody?

My granddaughter (daughter's daughter) is 16 years old. (will be 17 in feb.) and she wants to live with me. I have had custody of her 3 other times (for her kindergarten, 7thm and 10th grade year). She is unhappy at home and her mother doesn't want to sign over her rights. I just want her to be happy because she wants to spend her senior year with me around the people she love (brother, friends, boyfriend, & me). I was just wondering is there anyway I can take her to court or something where I can get custody?