Of course it is a betrayal, especially if whatever was disclosed was disclosed recklessly. I can actually relate to this because I did something like this before but it was with good intention. I informed a relative of some information that I felt would give them a heads up on "the reason for their childs behavior". This was information that I knew because the person shared it with me. Instead of using it productively, they chose to tell the person what I told them, making it seem as though I betrayed them, just to severe whatever relationship they were jealous of. That is why it's not worth it to help or get involve in helping people because you never know their intentions or their heart (unless you really know them). If whatever information was disclosed recklessly with mal intent, your best bet is to remove yourself from that person forever, it doesn't matter who they are!
Ooops I read your question wrong....nevertheless I will leave my comment regardless if it is sort of off topic. To answer the question to some degree it is but it's really not that serious because whatever was supposed to be discussed was not discussed elsewhere.