High School romance

Im a senior and during the year I have been talkig to this girl I really didnt like but after awhile I liked her. Fast-Forwarding to may 9 i had a fight with her because I thought she was cheating with a friend so I kind of ignored her. After that things got a little awkward. A month later she is with that guy I mentioned earlier. Obviously I will get rid of her but how should I approach her about this without losing the power? Do I make her feel guilty or insult or just tell her? Btw I am not the kind of guy that believes in love so I get over this things in days and as soon as I approach the matter at hand? He is also kind of my best friend so what about that? And is less than a month a short time for getting in new relation right? That means she liked him from before and not me.

I would actually just ****ing ignore that hoe. Period. Dont talk with her and start talking to other girls. Thats how you will hold your power. By being independent from her. Secondly I would actually talk to your bestfriend. I mean did he know you liked her? Did he just dont give a **** about you? Its not really like he took your girlfriend. Probably he just wanted to taste *****. If it was me I would have given him the chance to hook up where I failed. But the best thing would be to talk with him. I hope this helps.