Hi Nina,

I’m not sure why you feel back stabbed. Are you sure that it was clear beyond any reasonable doubt that that information should have been kept confidential between you all? If you are all starting some kind of company or activity, it may be the source of good publicity that is going to benefit you all. Did you read the small print in the contract? What was their explanation about their behavior? As Elle said a confrontation would be good.
If you really believe they have been mean to you or they seem to not understand what pain they caused, then protect yourself. Do not give them any more information about you, do not leave your personal items around when they are close by, try to deal with them as little as possible. Clean any pending debt and move on.
If you want to differentiate, get to know your allies. What do they think about the fact that they posted your sensitive information without your consent? Once you know, bring them away with you. I’m sure they do not want to risk being back stabbed themselves. Maybe, as you inquire, you do not want to look too much disappointed since, maybe, you do not want to alert those who may not be your allies. Maybe you can ask them what they think about something similar that happened to somebody else or what they would think if that happened to them, just to get a taste about what they may think.