I had a temper growing up and used to lash out. This was what happened at school, when bullies would deliberately wind me up until I couldn’t cope anymore and would then hit them. (They were never really hurt.) It was always me who ended up in trouble, because I couldn’t put into words the way they were tormenting me.
No, that doesn’t justify my behaviour. But it wasn’t a case of me being an abuser; their whole strategy was about getting me into trouble by provoking me into lashing out.
My DSis did this to me at home, which she herself has long since admitted to doing.
Like the OP’s friend, I was vulnerable in that I was being sexually abused at home (so was my DSis). Did that mean that I was justified in lashing out? No, of course not. But I’ve seen the same pattern in my DD1’s (12) behaviour as well. (She and DD2 (9) are both adopted, so they’re both vulnerable.)
So I don’t agree that this is clearly a simple case of the OP’s friend being an abuser and her husband the victim. It could well be the case that he’s actively provoking her with mind games.
On a positive note, as an adult I don’t lash out anymore and have been able to process my anger during years of therapy. It sounds as if the OP’s friend would benefit from such help, and she needs to reach out for it, both for her own sake and for the sake of her DC.
Meantime, she does need to get out of the toxic relationship she’s in. (That’s what really matters here regardless of whether the friend is an abuser or a victim. It sounds far more complex than that.)