Which party should i go to?

Ok so finally the guy i like invites me to go with him to a party. Everything was perfect. But my bestfriend (since kindergarden) wasnt invited, but she ddnt know about the party anyways, the thing is that her birthday is next week and shes doing a birthday party , so she invited me. But her party and the party i was invited to ar� the same day! And i don't know what to do, because i waiting so long for the guy which i really like but ahe is my bestfriend. I need help!!! Which party should i go to? What would you do?