I think my group therapist broke my confidentiality right. can i sue her?

I go to this group therapy thing called dbt. And today my therapist (group leader) left the room on break. One of the girls pulled out a little baggy full of pills, (she said they were adderall) gave them to two other girls and all three of them are 16. I ended up telling my group leader in the hallway (yes I know I'm a snitch, but I was actually worried about their health). My group leader pulled them out of group and made it completely obvious that I told, then proceeded to tell them that I was the one who told on them. They're now extremely angry at me. Doesn't that break confidentiality? And if so what can I do about it? Will I be able to sue her?