My Easter Egger stops laying for long periods of time because of flock stress--even when she isn't at the bottom of the pecking order. When I remove her to a separate, safe location, she gets back into lay. Point: maybe she is feeling stressed? I would try separating her for a while and see if it helps. One word of caution though: if she isn't at the bottom of the pecking order now, she will be when she gets reintegrated with the flock...which should be done carefully.