I have a medical question that pertains to privacy.?

My wife is in a aftercare program for alcohol addiction. She was sick the past couple days with a fever of 100 and GI trouble. The other patients in her group doubted her sobriety and gossiped about her relapsing. One of them went as far as calling my wife at her mother's house. They have an unlisted number so the only way for them to call her would be if a rehab staff member gave it to them. Is this violating my wife's privacy? Isn't there a law against giving out patient information?