Not invited to a party!!?

well this girl at my school (it was her first year here) is having her birthday party tonight. i wasnt invited. to be honest i didnt invite her to my bday party & i never have even really talked to her and im not in any cles with her and shes not in my homeroom. but the thing that bothers me is that she invited most of my friends. like some of my friends werent invited but other than that all of them were. i'm pissed off. i know i shouldnt be that mad because i dont even know her but still!