I feel betrayed by my friends, what should I do?

OK so a little background: my girlfriends are really big gossips they love to get into everyones business and it can get kind of annoying. So I have this one friend that Ive known for a few years and we were roommates for two yrs. We are really close and for the most part ive been able to depend on her to keep things confidential, things including a pregnancy scare. So I thought I could trust her. Ive been feeling really depressed lately and have been suffering from insomnia, so I told my friend this and went into detail about it and I told her I made an apt with the school counseling center and that I was going to make some changes for the good. I called her the next day just to apologize about throwing all of that info at her at once, and asked her to not tell this one girl that has a huge mouth... well she had already told her!!! Which was one of the things she knows bothers me- people talking about me behind my back. Its not like I told her I was hurting myself or anorexic, and she knows that I realize I have a prob and that im working on it. She claims she did it out of concern.. but I don't understand how telling a blabber mouth my problems is supposed to help even if it was out of concern. Do I have a right to be mad? Do you think I should talk to her about this? Shes very sensitive and I know it will hurt her feelings but I feel extremely betrayed by her and I don't plan on telling her anything anymore.