Seems that with #1, there's nothing you can do other than be there for your friend.
I can not understand why young people today put up with so much garbage while dating.
With #2 that guy is a class A jerk and should be dumped. It 'sounds' like your friend is sticking with him BECAUSE of his popularity or something. If his friends 'hate her' *and I can speak from a little experience on this one* then something's going on behind her back. There's obviously a much bigger, uglier picture there, trust me. She needs to move on, get away from him.
The only thing YOU can do, is be there for your friends and be honest when they turn to you and ask 'What should I do?'