I think this is more of a 'what is your style at work' type question.
Long story short a coworker received information about one of my programs from the customer. Not a big deal, but instead of just passing the message to me and giving me a heads up (which she should have done) she decided to contact one of her friends on the program and ask about this issue, then let me know, and then walked down to bring this up with my boss. I am annoyed by the situation but the PM is pissed. PM wants me to make it clear to her that in the future she should basically not do this.
My general style is to try and stay out of this type of stuff and keep peace, so I will probably not bring it up with her. The PM might bring it up with our boss, but I don't think it my place to tell him. DH thinks I'm crazy since he is in the military and tends to call a spade a spade (I remind him that I can be fired though). Do you say things to coworkers when they are out of line, mention it to your boss, let it go?