A friend

I have a friend. We consider ourselves sisters because both of our sisters live far away. We talk about many things that most sisters would. On more than one occasion we talked about things that I thought would stay between us only to find out that she told someone else. It got to the point that I started limiting what I told her because I couldn't trust that it wonldn't be repeated. I found out this evening that it happened again. I told her something that I didn't even think about being repeated. And she talked. It really upsets me. Honestly, it makes me angry. Not only because it makes me look like a gossip but it effected someone else. If I wasn't so nonconfrontational I would say something. What's the worst really...she'd repeat it?!