I am sorry to say that I am in the situation your friend has been through. I can now recognise his awful behaviour, and I am starting to believe it isn't my fault and that he just has issues. However, he has completely destroyed my self esteem and for a long time I have believed his actions were the result of my own wrong doings. He often belittles me, he will scream at me, call me ugly, fat, stupid, a sl*g, when I am completely faithful and devoted to him. He will ignore me, out of the blue, pick holes in small things I do that he sees reason to escalate into a huge argument. I no longer have male friends ans i dont go out much. He often says everyone hates me, both his friends and my friends and the wider community!! My mother has terminal cancer, if I ever feel down or upset about that he says "why are you bothered? It's not like she's going to die tomorrow" and other unsupportive things. I am only just beginning to recognise this as a form of mental abuse and bullying. If all this was true, why does he bother with me at all???
for some reason, unknown to myself, I crave his affection and I desperately want to make him proud of me. (For any psycho analysers out there, I have always had healthy relationships in the past and my relationship with my father couldn't be better). So if things did end, I would be devastated like your friend, despite my friends and family believing I am well shot of him.
eventually though, time is a great healer. And so in time, your friend will have better understanding and more life experience to really see this man and the situation for what it really was. This man clearly has insecurity and other issues that are not in any way your friends fault. I would put money on your friend being a beautiful, kind, intelligent girl, hence why this man was attracted in the first place. However, he clearly felt threatened by her and so took to destroying her (he probably did not even realise he was doing this, I am sure this will be "normal" behaviour for him).
at the moment, your friend is still in a grieving place, but she is grieving for an idea rather than a person which is often harder as there is nothing that is true and so she will have many doubts.
the best thing she can do is keep busy. Throw herself into work, seeing friends, a new hobby. do this with her, do not allow her to dwell. Do not pressurise her to see other men, that will make her feel guilty and possibly ashamed and he will definitely use that as leverage against her. Only when she feels ready and has met someone that she really likes.
I would also recommend changing her number, so that he can no longer contact her out of the blue.
give her a few more weeks and if there is still no improvement, she may be depressed. That again can be overcome in time, however a low dose of antidepressant may e helpful to boost her mood and allow your friend to think more positively. She will not be on medication forever, I myself took antidepressants as at first I found my mums diagnosis too much to bear. I was on a high dose 40mg and now have weaned myself off them and take none and feel so much better (except the relationship issues!!)
i know I am in the same situation, but I have to realise on my own and be ready to walk away from this man. Some days I do and some I don't, I still hope he will change. Your friend needs to and will realise that he is just one man, one quite pathetic one at that, and that there will come many others when the time is right. She got along quite fine before she met him and will do again!!!
i do hope this reassures you at least a little. Xxx