Best friends.

Ok so my best friend of about 9 years, basically like my sister, just told me I'm not invited to celebrate her birthday with her because some of her friends at her school (we don't go to the same school) don't like me because apparently I'm "rude". But I've only been near/met them once and I was being kind of shy so I didn't really talk.. is that rude? Also, it's like a tradition that we always celebrate our birthdays together and I didn't really want to break it.