The problem with domestic violence is that it's something that escalates, and in most cases neither the victim or people around them understands the situation as DV until it has gone on for such a long time that the victim feels "locked in" and perhaps don't see any way out, as their self-worth/self-esteem have been crushed step by step by their partner.
The first stages of DV are perhaps just verbal, or a box on the ear, and if the partner asks for forgivness and promise to never do it again, it's easy to not see it as DV, and that it's time to leave the relationship. When the DV goes on to be so severe asin this case, I can see why she might be so afraid that she can't see a way out anymore.
I work in the health care sector, and all personel had to take a web course about domestic violence arranged by the National Centre at Uppsala University ,
Start - The National Centre for Knowledge on Men's Violence Against Women (NCK) - Uppsala University, Sweden It was very good and an eye-opener for me about DV. Even if the name is men's violence against women, it's not only about that, it's about all kinds of violence in some kind of a relationship, for example against elderly persons from their carers. On the Swedish version of the site there are short videos about how to talk about and ask about relationship violence with clients/patients.