Hey there,
I'm so sorry that your in this situation. However, none of it is your fault. In fact what you've done for her is amazing. You were there for her when she needed you. You should be proud of yourself that you did as much as you could. Don't blame yourself for the mistakes of the authorities.
I agree, I do think you should try to get intouch with her by any means possible. Call her house. Go to their house. Talk to the police. In situations of abuse they should be checking up on her frequently, if not removing her from the situation. See if they can tell you anything. Tell them you haven't heard from her since that night.
My heart goes out to you. This is in no way your fault. You did an amazing job supporting her. Please
PM me if you need to talk.
Take care.