Now that she is showering her pistils, does this mark the beginning of pre-flowering? Also should I begin the switch from vegetative nutrients to flowering nutrients or keep with the vegetative nutrients until more pistils show?
No, not yet...She is just showing her sex. Not flowering. Wait until you start to see more growth at those site and at tops where buds form. You will start to see more, thicker white hairs appear. Start adding bloom nutrients then. Try half bloom/half grow for the first couple of weeks into flower then just bloom and any boosters you are using.... Good luck