Maybe mix them?? Or you could offer oyster shell seperately and she will eat it if she needs it. I would guess that her eggs will be very intermittent right now, and she may even stop for a while and restart at the right time...or maybe you just have an early bloomer...lucky you!
I would start your pullets on layer if one has laid an egg. It won't hurt at this stage. They are probably laying a bit early because its the maximum time of year for day length. Layer feed will make sure they can cover egg laying while still growing. You could also have an early maturing strain.