Random Sauces From All Around The World
according to Wikihow is…
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.
and I guess the best thing to do is to limit your contact to that person as minimum as possible.