I have a friend who is in a relationship with a dangerous man and I'm really worried for her. We're not super close but we're a few steps up from acquaintance. We met at work and occasionally socialise in the same groups, we're friends on social media etc but we're not close enough to socialise just the two of us.
She started seeing someone about 6 months ago, I happen to know of him and his reputation. He's spent time in prison for DV (pleaded down from attempted murder to a lesser charge) and is known to be violent and aggressive as well as jealous and controlling.
She is completely in love with him and he's convinced her that his prison sentence was a miscarriage of justice and he's not the person people think he is, however I know for a fact this isn't true. I've seen evidence of this violent behaviour since they have been together. He has completely 'love bombed' her and is about to move in to her house. I've spoken to her and told her what I know and what I've seen but he's convinced her I'm making it up.
He's already isolating her from her friends and she no longer speaks to me.
I know that she's not told her family about his past, because they would not approve and would be concerned for her. She told me this when she started seeing him.
Would I be unreasonable to email her sister telling her what I know? It's really worrying me because he is a very dangerous man and I believe she is in danger.
if I did email it would have to be anonymous as I'd be really worried about him finding out but I'd feel better if her family knew and could at least look out for her. At the moment they've no idea.
Or should I just stay out of it as we're not that close anyway?