My Friend Sorta Betrayed Me.Help?

okay so i have this crush on a guy in my cl :) and i told my 2nd bff named marisa. my fist bff is sorta a blabber mouth xD anyways i told her not to tell anyone. but she told this girl. im not that close with her and stuff. and i played truth or dare with marisa and she said i have to dance with someone if they ask me at the dinner dance. i said sure as long as its not gross. she said u still have to dance, i could tell luke ur crush. luke is like a girl. tell him bout crushes he'll spread them in 5 seconds flat. but the guy i have a crush on like marisa and she flirts with him in front of me. idk if shes a true friend, i mean she's always been there for me, but i just dont know. Help plz? tell me wht u think. thx :)