boyfriends sister attacked me

So my boyfriend and I have been together a little over a year and a half and have been living with each other since March. His sister and I have always butt heads but never anything serious. She never liked me and made that obvious and even told me that ill never be family and I'm "taking her brother away from her." I've tried to have a good relationship with her and talk with her but she always turned me down. There were some issues before where she tried to fight me but I obviously didn't want to because I love my boyfriend and I knew that would break his heart. Well, on Halloween she decided to come to my door mad for whatever reason. No one was home besides me and her so I was confused why all of a sudden she wanted to come in mine and my boyfriends room to talk to me. She starts yelling at me to come out of my room and "be a big girl." At this point I'm like "ok wtf is wrong? what did I do?" So I call my boyfriend to ask him what I should do because to be honest I was a little freaked out. She's 180 lbs and I'm 100 lbs, literally. After about 5 minutes of me telling her to please leave me alone and my boyfriend on speaker phone telling her to leave me alone. She then, burst through the door and started swinging on me. I was completely taken back by this because it was completely random. I didn't know why she was so mad at me especially since I haven't talked to her in so long. She then fought with me and I fought to get her away from me. Keep in mind that when that happened I didn't have any bumps or bruises. Just as I think everything's over and I'm walking away she comes up behind me and grabs my hair to pull me down and started stomping on my face. At that point I was scared for my life. She wouldn't stop and kept telling me how much she hated me. I finally got away from everything and picked up my phone with my boyfriend on the line and he's screaming at her to stop, he was on the phone the entire time. I walked out of the house to try to find someone because well, look at the picture.

I was scared that she gave me a concussion because I started to become disoriented. I also lost a good amount of blood from my nose. My boyfriend came speeding from work to me to take me to the hospital. The whole time he's screaming about how mad he is at her and crying because how bad I looked. When all was said and done at the hospital they told me I had a broken nose and a contusion, which considering the circumstances isn't that bad but still. I chose to not press charges because I didn't want even more problems to arise. My boyfriend and I moved away the next day and we haven't seen her since. She posted on social media about how she "beat my ass" and people were laughing at me from it. I had to delete my social media for the sake of my mental health. Ever since all of that happened, I haven't been able to get out of bed or stop crying. Im confused as to what I did to deserve all of this and why she waited till no one was home to come to my door. My face is healing fine but my heart hurts. For me but especially for my boyfriend.

UPDATE: When I was at the hospital and talked to the deputy, I told him I didn't want to press charges. I changed my mind after the social media stuff and called up to the station but they told me they couldn't find the report. The officer I spoke with offered to meet up to take a statement but I figured it was pointless since there's no record of the report. I'm 18 and don't have either of my parents so I have no idea how to go about anything. Thank you all for your kind words. Its appreciated tons. 😊💓