Why family or friends back-stab: trying to understand why some people “back-stab” or double-cross …
A backstabber is someone who pretends to be your friend, or to be on your side, and then turns around and does or says things that lead to you being harmed, exposed, or treated badly as a result of things they suggest or reveal.
Backstabbing is a form of manipulation and reveals a person who is disloyal, insecure, and very unsure of their own place.