My Sister’s Ex Husband Hit Her

My sister got divorce for an emotionally abusive husband. They have a child together that they share custody of. My sister believes that the child not safe when with him. He has no female in his life and all his friends are creepy.
My sister takes the child to father almost everyday after work. And that’s his chance of pressuring her to get back with him. In the process he has hit her three different times. He’s always asking for money and has taken all the child support($300/m) back.
My sister is doing her medical residency and her schedule is very strict. I’ve told her to make a police report but she hesitant because she’s been failed by the system before. She genuinely believes she won’t get any justice. Plus she says she has no time to go to police station or any lengthy procedures.
I really want to help her through this situation. Any advice on what could be done.

P.S. The important part that I missed is that the medical program my sister got into is in another state. Which means she’ll need her exs permission to take the child with her. But he’s only giving consent verbally. My sister says she’ll have to put up with his crap for at least these 3 years if she wants to complete her training.
The ex understands he has an upper hand and wants to take full advantage of the situation. He has been asking for money non stop so my sister had to give him back the child support.

So my question is what can she do in this scenario? Would a police report of abuse require an evidence?
Location: VA