I need to help her

Texas. My 17 year old niece moved out of her mother's house and into a house with a 22 year old man who is a registered sex offender. He's also physically abusive. She just found out she's pregnant. He has choked her, slammed a door on her so hard it put a gash in her forehead, and now, tonight, he kicked her in the stomach. My sister called the Sheriff in Angelina County but he went out there and told her there was nothing he could do because she started it. Is this legal? Does my niece have to press charges? What can I or her mother do? I'm desperate. I want to go there and take her away. She has said she wants to come live with me 3 and a half hours away from him but I think she's afraid of him. What can I do?

She can file a complaint with the local police or even seek a restraining order if she wants him to keep away.

The local court has forms and it is easy to file.

It sounds as if it is best she have no further contact with him based on what you say here.