Can I do something about this or should I just let it go?

Before summer vacation started I found out my best friend might be moving to live with her mom.
I do not like her mother. I don’t think she should move with her, yes it is her choice but would you go back with someone who beat you?
One day her mom got drunk and did, she called the cops on her and they gave custody of her to her dad, he is a nice man, and takes good care of her.
A few days before school ended she went to court for a hearing, she choose to live with her mom.
I’ve tried to talk her into living with her dad but she says she needs her mom too, I get that.
But her mother ignores her at times like this one day she went with her and she said she didn’t want anything to do with her. Then the next week she calls her up and takes her out. And she agrees to go.
What should I do? Can I do something at all?
I’ve know her for 5 years now so we are pretty close to each other. We go everywhere together and if she moves it will destroy our relationship.