This often happens, what seemed more than big enough when the chicks were tiny balls of fluff, is not big enough when they become full size, and complicate that with the very short days/long nights of winter, and you have birds in a tight quarters, bickering and fighting can break out.
Those darn coops greatly over estimate how many birds can fit in there. Always solve for the peace of the flock, and your flock is telling you that you have too many birds in there. Did you notice a reduction of tension in the flock when you pulled her? If not, you might need to re-home 2 birds.
I would sell this bird to another flock, and watch your remaining flock closely. It is always the bird you like best! darn it.
Mrs K