Well it is possible to flower your plant until it shows sex and if its female you can choose to put it back into vegetative, but I think too much time is lost with the plant re-adjusting to the light cycles and whatnot. I have never seen anybody with a plant 6-8 weeks along in flowering that put it back in vegetative though. My advice (and many others) is if you want a mother plant, take a clone from it, root the clone, flower the clone until you are confident about the sex. If it is male, get rid of the clone and the plant the clone came from ASAP, if it is female, get rid off the clone and keep the plant if came from in vegetative as your mother.