A lot of posters are saying 'imagine if it was the other way around'. I get the point being made but it's not as binary as that.
It really isn't the same, to compare every situation of partner violence with reversing the sexes.
This isn't excusing female abusers. And they do exist.
But there is a far higher likelihood of this relationship being abusive emotionally and mentally to the woman here. It is hard to imagine how that feels, and in general (note emphasis), that is perpetrated more by men to women.
It is not right. But her reacting physically to continued abuse can be understood & in the torture that that type of abuse is, can feel like the only option. (It's not right, again).
It isn't as easy as ' reverse the sexes'. A man has far more physical control, even without hurting his partner, than a woman. If a man was being emotionally abused by a woman who got in his space constantly, he can stop her without violence; a woman cannot, usually.
If he did start hitting her, that is more serious than a woman doing the same due to the physical imbalance of power.
I need to say that I am not justifying violence, saying that women can't be abusers or that men can't be victims of abuse. At all.
But the situation especially with emotional abuse and coercive control is very nuanced and very hard to understand if you haven't experienced it.