How can I help my twin sister get out of legal trouble?

There was a situation a few weeks ago. My sister and I were out with other friends at a club. I was dancing with a guy and was unaware he had a girlfriend who was there. She followed me when I went to the restroom. She told me not to dance with him again and pushed me to the ground and broke my high heel. She then wanted to fight with me. The problem is that I am really feminine and can't fight at all. I got up and told her that I was unaware he was with her and left the bar. She followed me to the parking lot and splashed a drink all over the back of my dress. I asked her not to hurt me because I am so weak. She then approached me aggressively and I stuck my arm out try and keep her away. She twisted my arm and pinned me against a car. I started crying and screamed for help. My sister who is much more of a tomboy and way stronger than me heard what was happening and ran out as this girl was about to beat me up. My sister hurt the girl really bad and put her in the hospital. Now my sister is facing ault charges. How is this fair? This girl was being a bully and picking on a wimp like me. My sister only got involved because she knows better than anybody that I can't defend myself because of how physically weak I am.