No matter what anyone else says, Sweetie Belle knows that whatever that is in the mirror isn't her. That doesn't mean she can do anything about it.
An entry to the seventeenth Quills and Sofas Speedwriting Competition. Written in sixty minutes. Prompt was "Mirror" and genre was limited to horror. Presented here as is.
Now with a Russian translation, thanks to NovemberDragon, Randy1974, and Nuclear-pony-Jack. Find it here, here, and here.