You probably have 2.5 weeks of stretching left at a minimum.. My try at LST with a tall (6.5') Tangerine Dream, it snapped at mid-plant taking over 2' off the top. I chose to kill it. You'll find sativas tend to get pretty big and spread out like a christmas tree. If you want to grow them, best to clone a mature female, don't veg too long and depending on your head room make sure you have enough room under your lights for it to triple in height during flower without getting burned. Also, don't over achieve on container size (assuming you're in soilless mix or similar); the more room you give the roots the bigger the plant will grow.

Admittedly, I'm not the best source for LST advice. I can tell you, vertical or horizontal, it will reach for the light in a big way.. How long are you estimating it's going to take this girl to finish? My G13 Haze was taking 12-13 weeks.

Farmer Rich