Is my best friend replacing me?

[Izzie]

I'm best friends with my best friend for a long time now. We have a lot in common, but we also have opposite tastes and opinions. It never bothered us. But recently she has been doing some stuff, maybe irrelevant, but that made me feel like crap. She was the only person that didn't call me to say happy birthday. She didn't say nothing at all, not even an message on facebook. She has been a little cold and distant when we talk... And she called her other friend best friend on facebook alot of times. I know it's stupid but it kinda hurts me, you know? Especially because she tagged her two other friends on twitter with the tag #WhatILoveAboutMyBestFriend.. and didn't tag me.
I dunno, what you guys think? ;/