I have a friend that I know through work, although that friendship extends to outside work as well. Over time we've built up what I thought was a good friendship but I've recently found out that the manager of the department where I work uses her as a spy, to find out what is going on in the department where I work and also in other departments around the building (my friend has the reputation of being a fun & sociable who everyone loves) Earlier this week my manager let slip something that I had discussed with my "friend" and which was private. The manager herself admitted another of my friends, who she has been mentoring, that she uses this person to find out things that she'd like to know.
I don't want to be this person's friend anymore. Am I over-reacting?