Good advice to keep a distance and never trust them again. Ever. I truly feel backstabbers almost can't stop themselves. Even if they move on to another victim, if you're in their circle (at work, or whatever), they can try to involve you by inferring you're to blame or somehow a party to it.
A coworker and I discovered an Office Snake was backstabbing both of us and trying to shift blame onto one or both of us. We confronted the little rat, and although she quickly backpedaled and never again tried to pull such a stunt, neither of us trusted her from that point forward.