She may be staying in the coop to get away from the bullys. The chickens at the bottom of the pecking order will find a place to "get away" from the meanies. I have two girls and one roo that also stays in the coop until I open the run door and allow them to free range. They are going to be rehomed to a 2nd run and coop shortly. They are low on the pecking order and stay in the coop to keep away from the others. Maybe yours does too?My chicken keeps doing the same thing, but she stays in the hen house all the time and I don’t know what is wrong plz help