The wound looks good, as good as a wound can. If you have an avian vet near you they might be able to strap her beak back so it grows properly. If not and she is still able to eat I would give her a chance. If your worried about her pain, here's a link about drugs to make them more comfortable https://www.backyardchickens.com/forum/viewtopic.php?id=239791
I just had to Cull my favorite Roo Aggressive and mean hurt 2 of my girls and attached me!
They don't get better i have put up with it for months so do yourself and your girls a favor and
get him away from them!!!
If you are sure it was the rooster I'd get rid of him. A lot of roosters do go through an awkward stage where they are not very talented at their "job" and some may be rougher then necessary at first. Good roosters grow out of this and learn how to be a little more decent.
It looks like he may have been trying to grab the back of her head and missed? Poor girl. Not sure how she'll do with that lower beak hanging like that. Is it mobile at all or just hanging there?