Wedding Change Date?

My best friend of over 15 years is getting married next year..they have had the date set for 2 years..I Reciently got engaged to her cousin .. We have decided to have our wedding next year in the spring... It happend to be before hers and she has asked me to change my date and not plan anythign untill after hers is over,that this was "her year"....I told her that my date was set and have no intentions of changing it.since then she has not talked to me.. And some of her family has been cold to me.. Was it wrong of me to refuse to change my date or is she just being slefish?