This is to refer to a person who goes out of their way to betray peoples' trust. They are mean and go out of their way to be so.
That person is a Two-Faced Snake because they decided to go behind my back and betray me.
A two faced snake is a person that is like a best friend to you when no one else is around but when with their friends they act.
Fred: Ill meet you at the bus stop.
Joe: Okay I'll bring tom.
Fred: Don't bring Tom, it can be just us.
Joe: If you say so Fred don't be a two faced snake again please.
~at the bus stop
Joe: Didnt you say not to bring anyone?
Fred: Bro who are you stop talking to me lmao embarrassment.
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