friends suck.

dont you just hate it when you have a best best best friend, and then they ignore you when their other friend is around?
well hatred doesnt cover how much i dislike it.
here's what happened;

Steph, Fred, Matt and i were going to meet up at a festival in town called the Buskers Festival. but Steph invited this other girl to go too, Cassandra.
when i got to the festival, my friends were sitting on the dirty curb of the street, with cigarette butts all over, beside these two really loud games, one of them involved trowing a ball at beer bottles.
i sat on the curb with them for a little while, but the entire time, the who i had thought was my best friend, ignored me.
so i got annoyed and walked off to find some other friends to hang out with.
i came back a few hours later, and shes pissed off at me for ditching her, but its time to go home, so nothing really happens.
then yesterday, Fred and Cassandra come to my door and ask to hang out at the park, when i get there, Steph and Cassandra ignore me again. after about like 2 hours, i decide i wanna go home, and when i'm leaving Steph calls out and asks me whats wrong.
i ignore her, but she comes up to me and says "are you mad at me?" i say yes, and walk away.
i saw her later on that day, and she pretended i wasnt alive.

what should i do? D: