Sounds like she's in shock or grieving. I lost 4 hens to a neighbor's dog and my 3 surviving hens did almost the same thing as your pullet. For several days they just stayed in the coop/run not making a sound and hardly moved at all, my rooster had his eyes closed most of the time. It was several days afterward when they finally became more active and eating more but almost a full week before they started acting like themselves again. Was your pullet sick or injured before she passed? If she was sick, keep an eye on your surviving pullet for any signs of symptoms, sometimes a sickness can be passed onto others in your flock.