How to peacefully end a friendship?

I originally tried to ask this question on yahoo answers, but for some reason it got deleted soo yeah,
So, I have a best friend,but lately I have been ignoring her, which I know has probably made her upset. For instance, last night I asked in this group chat that me and my friends have “if anyone was in the dining hall” and my best friend replied “yeah I’m here with Sara and Chris”. A little part of me was a little bothered that she went to the dining hall without inviting me, because usually I do that with her and my other friends. Anyways I went to my school’s dining hall and I sat at the table she was sitting at and realized that this guy she has been leading on was there too which bothered me. I proceeded to ignore her the entire time and I didn’t talk to her. I think she realized I was upset/ignoring her and decided to leave with the guy she’s been leading on and his friend. I think part of me is upset with her because she’s been leading this guy on/reciprocating his feelings, but then she has a boyfriend back at home that she says she loves and I do not agree with how she is handling the situation. She’s let this guy sleep in her room and has allowed him to be touchy feely with her when both her, and the guy, know she has a boyfriend Anyways I think even if I was honest to her about my feelings, I do not think the problem would be resolved.And I think the problem is really just me.So, I think that it is best to probably stop being friends since I am being so mean, unreasonable, and hurtful( and I do not think I’ll stop anytime soon) I know I sound like a major ass and I honestly feel embarrassed for feeling this way,but do you mind helping me figure out the best way to go about peacefully ending our friendship?

The friendship has already ended.

I guess you’re ultimately right. I guess I was just hoping there was a less rude way to do it. Is it really fine to just end it like that? To just immediately stop talking? I do not want her to think I hate her/she did something wrong because putting myself in her shoes that’s how I would feel.

Just let is fade away. She’ll understand. Don’t ask for drama…

Yeah I mean there’s at least a couple routes you can take, fess up and tell her why you’re upset with her (difficult but may be the only way to find closure), or just let it fade like others have said. It’s a sketchy thing she’s doing, so ultimately if you don’t want that kind of bad karma (for lack of a better word) in your life, you can decide to just let her go. Sadly in college a lot of friendships end, but I think it can make way for better more meaningful ones. Hope all goes well.

I think she has already moved on. I hope you have other friends, because she might be happy enough with Sara and Chris.