Best Friends For Never

Okay, i've officially lost one of my best friends.
Me and her both know this certain guy at our school. I hate him. He's rude, sarcastic, moody, critical, and overbearing. And don't think it's just me that thinks this. Ask any other friend of mine besides HER and they'll tell you the same thing.
Anyways, for some reason, she found the need to ask him out. And after a month of taunting her about his answer, he agreed to give her one chance, like he was so much better than her. And after three weeks, they're still together. Barely. He orders her around and tells her what to do and teases her and all that crap, but she's so absorbed in him that she doesn't notice how he really acts. She's always talking about "Oh, he let me hold his hand!" and "Oh, he got a new shirt!"
Well I've tried telling her she's made a mistake but she won't listen. I'm done with it. I'm already dealing with ADHD, Avoidant Personality Disorder, and Bipolar Depression, so I don't need to be worrying about her on top of it.
But out of my group of my friends, I'm always the person that will help with anything, drop everything to help someone, and will even lie sometimes to make people happy. (Don't get me wrong, I'm not weak. I broke a guy's nose when I was in middle school because he made fun of my friend.)
Now I don't talk to her. Neither do most of our (now MY) friends.
I still see my former friend all the time at school and around town, but I don't think it will ever be the same.
The worst part isn't that she's still with him.
It's that she doesn't care that I have refused to talk to either of them for a month. Like we were never best friends for five years.