Boyfriend

My sister is always complaing how her boyfriend treats her badly and complains to me about it like every single day. Now it’s just annyoing, I tell her he isn’t good for her if he treats her like that. But she still goes out with him. He gets Fs in every class, he doesn’t have his driving permit yet and he’s 17, he had to repeat 8th grade because he doesn’t do his homework and he doesn’t have a job either.