Have you noticed girls seem to do this?

Like I will hook up with a girl and she will tell all our mutual friends. I get it...its free pre selection and therefore dread but its fucking irritating. As I am naturally a very private person.

Just recently a girl I started talking to (hadn't slept with yet) started telling everyone we were talking.

I don't get it. Are they trying to "mark territory".

Why do they do this?