That's the thing though, Buttwitch is (most likely) a manifestation of Reggie's fears of maturation.
It would make sense if that entity is at odds with Reggie and at odds with Endless.
But you have to grow up.
Buttwitch is evil, yeah, but so is Endless.
The show has shown us inadvertently that Endless is a nefarious place. It seems to swallow people up who need a place to escape. Either the villagers are complicit in Endless (as in they're a part of it), or they're people who became trapped and Reggie's on the path to becoming one of them if she doesn't escape.
Buttwitch is her escape. Grow up, stop going to Endless. Don't become a mindless villager like the rest.