Hi there.. if she's a photoperiodic then i wouldn't put her under 12/12 right away. actually i wouldn't do that to any plant.. first of all she will not grow much, and you're just wasting time and especially yield.. "12/12 from seed" can be done, but i really wouldn't suggest it to anyone. Just put her under 18/6 until she shows maturation (pre-flowers), which will most likely take a month or two, and then put her under 12/12 and you'll get a nice harvest.
Also 40/45% humidity is very low for this stage of plant, so you'll inhibit growth even more. In this stage you'll really want it to be in the 70's when the air temperature is 27 degrees C.
Read up on VPD, and then check out his VPD chart (check the temperature on the left and then look at the color for the various stages of plant growth on the top right and see what's humidity range is ideal for your plants current state): http://www.just4growers.com/stream/temperature-humidity-and-c02/vapor-pressure-deficit-the-hidden-force-on-your-plants.aspx
happy growing!