that's just how it goes. the trick is to never take it personal.yeah like @Turbulent said, happens when they get someone new.
when i was i remember this chick i was just smashing on the side, a "friends with benefits", then one day she stopped answering my texts, phone calls. I saw her at the mall with her friend and she just right passed me, anyways to make a long story medium she finally found some sucker to give up his vagina aka commitment