I betrayed my best friend
Why do you think that you betrayed her?
She was my best friend after all, she tried to kill me because of some reasons
So did she try and kill you due to the betrayal or was it the opposite way around? Either way, since you're best friends, I'm pretty sure you can calmly discuss your issues.
I just wanted some excitement.
Being bored is no reason to betray your friends. I think that a better route would have been to talk through the problems you are having.