prepare yourself for the big confrontation..

you should be able to answer the why's..
why did you betray me?
why do you have to tell others about your issues with me?
why did you not just throw it to my face?

explain and be ready for a good reason why you didn't tell that person in the first place like:

I didn't tell you because I know you will never admit that it was your fault..blah blah blah..

Good luck!
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L♥VE LIFE!