Is it normal i'm bothered when a friend mentions something i never told them?

Is it normal that it bothers me when a mutual friend of a friend, while we're having a one-to-one conversation together, mentions a somewhat personal fact or an experience of mine that I never told directly to them? Or brings up one of those subjects/experiences I had to change the direction of conversation?

I realize that all groups of friends talk about each other behind their backs, and this is how that mutual friend found out, but it just amazes me how little tact people who do this have. It's as if they want it to be incredibly evident to you that they had been talking about you and not caring about your feelings about these issues. There's no filter between the brain and mouth.

The time this bothered me the most was when I was an upperclassman at college, and my friend at the time became the resident assistant for my floor's dorms...hence she became my RA. I talked to my resident assistant/friend about some experiences of my past and some family issues here and there, and sure enough it got back to my roommate (who's also the resident assistant's friend), and she later mentioned these subjects in conversation several times as if they were to be casually talked about. I did not tell her about those experiences for that particular reason.

Does this lack of discretion annoy anyone else?