REPOST: Custody Question! Very serious need help ASAP!!!?

About a year ago my family began takin care of my cousin's baby who was then 9 months. We found out that her mother was lettin anyone keep her while she was workin or out partyin. My mom volunteered to keep her, when she came over we fell in love with her and didn't want her to go back to that life that her mom is still livin. She knew we were takin good care of her and said that she could stay with us. She only sees her like once a month, by choice & doesnt call til then. My mom doesnt want to let her go with her mom but she has to b/c we don't have legal custody yet. I know that her mom will not willingly give us custody b/c she is benefitin 4rm the state and my cousin, who the child's father.He gives my mom & dad money to provide 4 the child. He is goin to court to c if he can give custody to us, we have alot of evidence on what has been going on this past year, last week she came back wit a leg burn . I was wonderin do we have a chance in gettin custody or make things worst?? HELP!