Leslie is one of the villains in South Park, and is killed by the PC principal.

but... who is the "other leslie?"

this leslie with brown hair and a different shape. perhaps she is the real Leslie and the one we see as the villain is just a clone-ad.

the reason why?

look at that scene above where leslie (real) and a mysterious sister listen to lorde's music.

if she has a little sister it can really be her, because ads can't reproduce like humans,

so the fake leslie was killed and the real one is still alive.

and I don't know because she isn't in the subsequent episodes, the creators removed her from the BGs to make her death clear, but I think the real Leslie moved or changed class.

END!

Like the theory? :D