There really are people like this IRL. They need the high that being a victim or seen as innocent provides. And they'll get a mob to sic on you if they can. They love to push a snowball down the mountain and watch it become an avalanche. People fight each other and end up forgetting the cause.
A girl in my class tried doing that. I stopped it because I caught on quick. The key is to not retaliate and calm the other party down and let them see reason. Your non-aggressive CALM behavior will go against the lies she spreads in real time and they'll realize something is up. Unfortunately, they won't even realize the "victim" caused the problem in the first place because they idolized them. But at least they won't mobilize against you again. Everytime the "victim" tries again they are less likely to be successful because rapport is built between the resolved parties. And the "victim" becomes increasingly frustrated. It really is a battle of attrition.