Don't want friend to go back to her toxic relationship

I'D love to know how to help my best friend, who's finally broken things off with her awful fiancé.

- 

She's left him a couple of times before and has always gone back, but ending the engagement feels serious, so I think she means it.

She's told her family that the wedding is off, which is a big step. I think she realised it was now or never, as she was going to have to start paying for things like the wedding venue and so on.

She's not in a good place, though. She'd tried so hard to make it work with her ex, even though he didn't deserve it. He cheated on her twice during their relationship and all he thinks about is himself. None of her friends, including me, can stand him.