you should let it veg unti lit matures as suggested. Its not a good idea to take a cutting from an immature or child plant just to see the sex. This is like taking a 6 year old girl and asking her to show her tits and that's just rude and sick. Kidding aside you will not be getting the full genetics of the plant because its a child. This maturity is no different that puberty for humans in many ways, afterward the plant will show "pre flowers" this word confuses people because it is not a flower and is just the same girl showing sex plainly because the plant is actually old enough and has passed puberty, sometimes the branch nodes start alternating as well but normally you see the sack forming or the tiny hairs. At this point you can tell the sex of the plant without stressing it and it takes about the same amount of time as stressing the plant into showing sex before its even able to afterward as long as you keep the lights at least 15+ hours of light the mother plant will not flower unless it has some ruderalis in it. The main point is you would not want to establish a mother plant from a stressed immature plant as this is what you are multiplying plus it takes about the same amount of time to get it reveging. Take the time and do it right and you will be able to see which female has the best values as far as looks and growth rates, stem thickness. Later you will be able to tell if the smoke is kick ass and keep it going but trust me once you start taking cuttings you are in essence topping branches with growth spots and normally this splits into two so after two weeks you have twice the amount of cuttings to take and it very quicky turns into 24-36 clones every two weeks. I end up tossing the mother plant into flower room after a few cuttings as I have not been able to stunt the growth enough to hold it back. Good luck and be weary of the advice you get before actually trying things when it comes to "tricks" also take a look at the how many posts someone has made also is a clue sometimes (not always I have seen some excellent advice from people with very few posts) Again good luck