AITA.  Please forgive me as this is literally my first reddit post, ever.
        Back in high school, I never really had any girlfriends. I was starting to exhibit some incel “nice guy” traits that I’ve since been really embarrassed about, and it was a very awkward time for me. After having had crushes on a lot of girls and being denied every single time, I had essentially lost hope of being in a relationship/ having my first kiss, or whatever in high school. That is, until, this girl came along... we’ll call her B. 
        I had a science class with B and from the first day we really hit it off, she was engaging me, trying to talk with me, and it seemed like flirting a little bit. Now being a “nice guy” I never knew what it was like for a girl to flirt with me, and I took all female interaction as a sign that they wanted to date me. However, having had a really tough time with my previous crush, I really didn’t want it to happen again, so I actively resisted talking to B or even being near her, but she persisted, and brought me closer to her, which made me fall in love with her... big leap, I know, and boy was that a mistake. 
        At first we started with just friendly conversation in class, and eventually she DM’ed me on a group chat app, and we started talking for about two weeks or so. It was about this time that I learned that she broke up with her previous boyfriend, sometime after the school year began. It was someone she didn’t particularly like, and someone who often played with her feelings and emotions. But, she got back together with him about a week after we started talking. She was still talking to me, being somewhat flirtatious, and suddenly one day, B asked me a question: Do you like me? The answer was yes, and I asked her the same question, and her answer was also yes. 
         She told me she wasn’t happy in her relationship, and she didn’t want to be with her boyfriend anymore. But, she didn’t break up with him. In fact, she outright refused to. I figured she was afraid of something... or really just didn’t want to for one reason or another. But nevertheless, she said she liked me, and she wanted to be with me, so I hung on. She confided in me, talked about her problems in life and with her boyfriend, which were numerous, and I was there for her when she felt like nobody else was. 
         Eventually, she started phasing me out of her life, she started ignoring my texts, talking to me less and less, not engaging me in conversations, both over text and in person. I would invite her to choir concerts (I as well as multiple others in choir were friends with her) and she refused to go. I would try to reach out to her, and she would ignore me. Then, five months after getting back together with her boyfriend, he broke up with her. 
         She was totally destroyed, and I was there to pick up the pieces, and help her through a terrible depression that she was going through. About a month later, I asked her if she wanted to be my girlfriend, and she said no. She said that she still hadn’t healed from the break up, and that she didn’t just want to use me as a rebound, she wanted to have a “meaningful relationship with me” which I thought was perfectly reasonable at the time, although I was impatient. 
          Around that time, I had really bad depression and anxiety, so I started reaching out more to my choir friends, and eventually found a group that I could confide in. We called ourselves AIDS (Anxiety, Depression, Insecurities Squad) it’s cringey I know. I had a good friend in there since freshman year, named R. R had told me, in a group hang out, that about a week after I asked her out, B had drunkenly “hit up” R. R knowing that I had a massive crush on B, politely declined, and B apologized the day after. However, I was devastated. 
          I was totally offended that she “hit up” another guy when she said she had feelings for me and I had feelings for her. It’s not that I wanted her to “hit me up” it’s that in doing so, she totally invalidated my feelings towards her, and the fact that she said she had feelings for me. I felt totally betrayed, and I felt like she had taken advantage of me during the time that I knew her. In my eyes, she simply used me as an emotional crutch, confiding in me because she wasn’t being emotionally fulfilled in her current relationship, so she went elsewhere to me. I thought, that instead of just telling me she didn’t like me, she lied to keep me around. 
           I confronted her with this, and it went about as well as you’d expect, and she accused me of only wanting to have a sexual relationship with her, which couldn’t have been farther from the truth. In her defense, she was drunk when she did it, and she apologized. And we weren’t dating, so she had no responsibility to tell me what happened, or even that it did happen. Nevertheless, our friendship pretty much ended after that, and it nearly drove me to suicide, I’m ashamed to admit. 
          We haven’t spoken after that, although she tried to friend me on Snapchat one day, and I denied the request. 
          Currently, I’m in a happy relationship with my girlfriend who was there to help me after B and I had the falling out. She’s the most wonderful, beautiful person in the world. I often think about B, and I get very anxious remembering the pain I suffered from that whole ordeal, and it weighs on my mind often. 
          So, am I the asshole for getting offended? Did I ruin the friendship?

TL:DR - A girl I liked said she liked me, but wouldn’t break up with her boyfriend. I gave her a lot of emotional support. When she did, she said she didn’t want to get together because she was still hurt from the break up, but “hit up” one of my good friends. I felt like she used me as an emotional crutch, and she thinks I only wanted to have sex with her.