I'm guessing you grow in soil, so I'd have to say get her to a foot before flowering.
Grow it to 1 foot before flowering, and you may get a 3 footer. It can be hard to notice it growing if you see it everyday coz you get so used to seeing it gradually get taller, but if you take some pics at the beginning of flowering and compare them to the end, it can be quite surprising how much bigger they get.