Child abuse question?

Okay, my sister beat up my fourteen year old niece by slamming her head on the concrete and and her face, my parents picked her up and the next day my niece called DHS, and they made a report and took pictures of her and all that. Well this happened about 4 days ago and my parents are just now taking my niece to the doctor, they will probaby exray her head and stuff because her head made a crack noise. Anyways, my parents are scared to go to the police because they think my sister will go to jail, (which I want), but they are being stupid. I might have to take her and I'm not the one considered her guardian by DHS, my parents are according to DHS. Will the dr office sent the diagnosis to the police dept or am I the one that is going to have to go around and do everything? Also, we live in a different town from where my niece was abused, and I was wondering if I can just take her to the town my parents live in, and can I use our own pictures or do we have to get DHS pictures and report, and will DHS give this info to me or can they fax it to the police dept for us? Someone please help me with this, I want to do what is right and I don't want my niece going back to her evil mother.