Is my best friend worth getting upset about?

That happened to me in High School.. My best friend started dating this guy and i didn't think it was a big deal, at first... But after a while, we started drifting apart... He actually told me, "I'm going to take her away from you"... I was shocked, but that's exactly what he did.. We still spoke to each other, but it wasn't the same... That was 5 years ago, and now we never speak... I felt she showed who she thought was more important, so i didn't stress it... But i was very hurt inside... I honestly think you should be upset and express how you feel to her, when it's just you and her... Don't show her that you're jealous, just show her that you miss her and you don't a guy to come in between y'all friendship... Because when the guy is long gone, your friends are always there...