OP it sounds like you don't know much about DV so well done for trying to find out what you can and help your friend.
What she is doing is what is best for her at the moment and she's right. The most dangerous time for a person in a DV relationship is when they leave. She is 'hypervigilant' because she has spent years surviving and she is probably suffering from trauma.
She is most in danger when leaving and in the first year after leaving, that is when most women are killed by a partner or former partner.
She will have her child taken away from her if they find out she is letting him continue to have access. She will have been told this so as you can see, even the threat of losing her child, is not stopping her. She's terrified of him and she's also trauma bonded to him. It's a very strong pull towards him.
He's had years and years to break her down and threaten her. He may have convinced her that she can't cope without him. Victims of DV also bond with the aggressor because it's a survival mechanism, otherwise her and her child may very well be dead.
She has lived on eggshells for years, anticipating his moods so she doesn't get the crap beaten out of her. What she doesn't realise is that it doesn't matter what she did or didn't do, he would find an excuse to do it. She's been conditioned through terror tactics and that's very difficult to push through.
She is doing the right thing for her until he is locked up. Lots of abusers have gone on to hunt down and kill their former partners even though there are restraining orders - it doesn't make a difference. She is the expert on her own relationship as she's been navigating it for years. She may also be concerned about family or friends as abusers often threaten them as well.