In this scenario we have person A, person B and person C. Imagine that A and B get into a disagreement and B seeks out C to vent and get support (an extremely common phenomenon). C will be tempted to get involved by siding with B, telling B what B should do, etc. Yet, the disagreement has nothing to do with C. In fact, the only reason C knows anything about A and B is because B has sought C out and told C. This, in turn, creates problems if C approaches A and starts discussing A and B’s disagreement. A now realizes that B has sought out C. A was not part of the conversation between B and C, but now C may be expressing anger, concern, criticism, you name it to A about A and B’s conversation. This is absolutely crazy-making and a sure-fire way to insure that the two people A and B who are the original participants in the disagreement never resolve it between themselves.
Although difficult, if A and B have a disagreement and B seeks out C, C must remain outside of A and B’s conflict. This is achieved by C being empathetic for B’s distress but throughout, encouraging B to go back to A in order to resolve the conflict. In fact, C may actually agree with B’s concerns and distress regarding how A spoke to or treated B. However, C needs to acknowledge this privately within C’s own head rather than saying anything to B. Remember that the only reason C even knows about the conversation between A and B is because B has relayed the details and the information C now has is solely from B’s point of view.
The struggle with what the marriage and therapy field calls triangulation is extremely common but difficult to change. If you find you struggle with A, B, and C problems therapy can definitely help on a familial level, a friendship level, and a corporate business level.