need advice or opinions. long story.

So I met this girl a few months ago who i fell for instantly but my friend liked her. she had no interest in him and wanted to date me so I went for it. I care so much for her and we dated for a few months. During all of this time my "friend" had people threatening to kill me and basically made me fear to go anywhere. I know I shouldn't have done this to my buddy but I don't feel I deserve all of this. Anyway, more to the story, I've spent every moment with her and we both established we wanted a serious relationship and wanted this to go far. Last Sunday however I woke up at her house to all of these threatening texts again about how I am the lowest person in the world and they will kill me if I go to work and all of this again. It got to me this time and after I left her house I felt crushed and I text her and told her that I cared about her but they were never going to let us be happy and that I needed time to think and clear my head. I never specified that I wanted to break up but from what I said I guess it could have been taken that way. She begged me to not do this and told me that she would do anything for me. I stopped answering and I continued to get texts like I will always be here for you and I will always care about you and to hit her up when I was ready to talk. So later that night I got a hold of these guys threatening me and met with them and told them that i chose her over them and they would have to accept it and that they weren't my real friends and they had to deal with it. I text her later in the night and told her that I was done for good with them and that they would never come between us again and that she meant the world to me. Now she acted like she didn't want to talk at the time and that she was busy and we would talk about it tomorrow. Tomorrow rolls around and I ask when we can talk and she keeps putting it off until 3 in the morning I finally call her and she tells me she has slept with another guy to make me mad. I told her I was done for real then and didn't want to talk. She kept calling me and texting me again and said she would do anything to take it back and give her another chance. I was crushed the whole next day but I realized that she means to much to me and that I wanted to fight through this so I go up to her house to meet with her and instead of us making up and welcoming back each other it turns into this thing where I am the bad guy and she says what she did wasn't that bad. Now she says she needs time to think and get through school. I know this means this other dude is probably hanging around though. I guess I just don't know what to do I care so much for her but now its just like she has lost everything for me and I had to fight through those feelings and actually forgive her. I'm feeling embarrased and I guess I just need someones thoughts. Thank you.