SHUD i B MAD @ THEM?

ok so on April 16,2008, my boyfrend Brandon, and my frend Taryn were spending time wit eachothr. @ first i didnt care.But then aftr lunch, Taryn was sitting on his lap wispering in his ear n gigling. i startd to cry n evry1 seemd 2 care. i had the support of my frends and family. (my cuzn goes 2 my skool as wel as my sis) i felt bakstabbd n lyed 2. i need ur help. shud i b mad at both of em or him or her..... taryn didnt no we were goin out so ya that mite help but he did. so.........