@creative_writer totally, I definitely didn't mean to imply that it was an intentional manipulative act - more that one can feel manipulated into acting, possibly out of guilt, when one is presented with something like that. But I digress.
Two thoughts on the betrayal thing - first, on one level, can you share this experience with your psych without giving details of who, just what happened? That might not count for anything though and may still feel like betrayal, so my second thought is - if this family member knew that you were struggling with this, would they want you to suffer alone or would they want you to get support? Or if you like - would they prioritise their sense of shame over your need for healing?
Quite possible that the behaviour emerged as a result of overwhelming meltdowny feelings - often extreme emotions beget extreme attempts at resolving them. Heck, maybe this family member has noooo idea that their behaviour impacted you this much? Do you think things would be different if they were aware?