You have to let it go. You can't worry about her because it will literally make you sick because you will be helpless. If she doesn't want to talk to you then she will not accept any help you try to give her. It hurts like hell. It will hurt so bad that your heart will literally ache. You might even feel physically sick from the hurt you're experiencing. But, in order for you to be any help for her (like say she decides to talk to you again in 6 months and you feel like you can) you have to get better yourself. At this point the relationship you have with her has changed. You're no longer her boyfriend and shes no longer your girlfriend. The romantic line has been severed at this point.

Talk to your therapist openly about it and ask them to help you walk through the break up.

I have learned this the hard way through a couple failed friendships. The ONLY thing you can do is suggest for her to make a change (aka finding a way to move out of her abusive home) but unless she wants it, it will not happen. It is NOT your fault. There are plenty of people in her situation that come to the conclusion that the abuse is not fair and that they deserve better. Even if you were still with her, you can't make her realize that unless she wants to. That is why it is crucial you make the changes. If you make the changes and she comes to you as a friend, you'll be able to help her rationally. If she doesn't, you need to know you did everything you could for her and that you're leaving the situation with love.

I don't want you to ruminate on this too much. I did 3 years ago, and got so severely depressed that I ended up hospitalized. For me it took over a year for me to feel okay about that person and I still can't extend my hand in friendship with them. (I am friends w/his brother and ask him for updates every once in a while.) Did it hurt? YES! It hurt so bad that I thought I was going to die because they were so close to me!!! Did I survive? Yes and I know you can too.