My granddaughter hates me because of mom boyfriend?

my granddaughter lives with me because ,she doesn't get along with mom's boyfriend .she miss her 2 step brothers and mom, but boyfriend don't like her ,so lives me. after 6 months with me she begs mom to let her Visit,mom says but for 4 hours only.but when she comes home to me ,all hell breaks out ,she says it my fault,that I'm mean,ugly,I hear her tell the little girl next door that I was been ugly to her .she is so far behind in school she got f's on her report card .I make her study everyday and we are start to see grader coming up, I brought her new clothes ,make take a bath every night. I work a living ,I did have money in bank ,but I use it on her .the clothes she brought from mom house I throw away, they were trash.I"thinking about pack her things and taking her home .oh by the way I have temporary custody between me and mom .and mom can come and her any time but does she?