>>1
...This is drama? Does this even matter? No, really. Don't you have more important things in your life whether to fret over how a girl knew why you and your ex no longer are dating? Isn't that a good thing?
Is accepting that either can be telling as much truth, and wait until you naturally discover the truth x years laters really such a problem? It's also useful to automatically assume ignorance rather than malice. Your friend might have casually (without noticing) said some things that clued others in on the situation.

I don't mean to belittle you and your problems, I'm just confused... The priorities differ greatly from my own, you see. Not that I'm great in any shape or way.