Is it normal to believe if a secret is shared with one person it becomes public
My last girlfriend had a really weird family and I was wondering if anyone else thinks this is normal. She was telling me that her sister took sexy pictures and sent them to her husband but only after making him promise never to show them to anyone. Shortly thereafter he showed the pictures to his friends at work. Now she was angry with him because he did this, and when she told her father about it he sided with the husband saying something to the effect of if she showed him the pictures then they were no longer private so she can't be mad.
I think that's insane, in my opinion he violated her trust, I think her father is out of his mind but i'm curious what you people think.
is it normal to believe something shared with one becomes public knowledge for all?