Rant, needing advice!

Bailey
In a really messed up way. My best friend (she's engaged) wanted to go hang out with this guy and I ended up going too. We spent two days awake hanging out together and he was really flirty and I flirted back. Well she declared him off limits. Messed up right? Well what's even more messed up is she said it was because she had feelings for him. So we had to leave for a bit so I could help my mom with some stuff and grab a shower. Well when we got back she had the brilliant idea to try and talk to him about it. Well turns out he was going to ask her where to take me to dinner. Well she told him I was off limits because I was in love with my ex. Words were said and it ultimately ended with him calling her out of being selfish (for fucks sake she's engaged) and her crying because he rejected her. Well we left and went and got one of our other friends and stayed at my place. Well the next morning she told me to do whatever I wanted with him and I was like "okay cool" so we were smoking a little ganja in my garage when my sister came home. She was pretty irritated that it was at my house and I didn't want to be there so after my friends left he offered to pick me up. So I went over and he made me dinner and we were watching a movie when he kissed me. (Don't judge me) that kiss led to me sleeping with him. It was my first time but I was like "okay this will probably be a one night stand" but after it was said and done he asked me to stay with him and we've been together ever since. Going on three months. But while we were over there (before we got together), she cheated on her fiancé with him while we were all really fucked up. Now she says she's "forgiven me for being with him" but she still brings that up "as a joke" even though she knows it pisses me off. Did she even have a right to be mad? If she's so over it why is she still bringing shit up? I'm still pretty pissed because she was really cruel to me after this went down (called me a manipulative c***) but I got over it. I can't just drop her because she's been by my side through a lot, for 8 years. I'm just so upset and I don't know what to do.