<human>: My best friend is dating one of the girls I know, and it turns out she's horribly abusive. She hits him as hard as she can (which he plays off as a joke because she is so weak that she can't hurt anyone), and has made it to where he now reports his location to her. WE'RE IN HIGH SCHOOL. He can't hang out with me, and when she finds out that we do she gets super pissed. 

And it's not like she really cares about him-- she doesn't mind not seeing him, and when they're avoiding each other because he hates confrontation, she doesn't say a word to anyone, and I've no idea if she even talks to him about it. She even chooses not to sit by him in class. 

But he doesn't believe that his relationship with her is unhealthy, and I'm just asking-- anyone have any advice for him? I'm hoping that maybe if it isn't coming from me then he'll take it seriously for once.

Also, note: our relationship is so platonic that my mother (who makes fun of me for even acknowledging a boy's presence) doesn't care if i have him over alone. At all. She's talked to him, quite likes him, and couldn't care less that we're friends because she knows it's platonic.

Summarize the given text in a few sentences.
<bot>: My best friend is in an abusive relationship at 16, and won't listen to me to get out of it, so I'm asking for the internet's opinion.