thats 9 weeks???? looks small. what kinda light? what are your temps?
it looks like your leave stems are purple, this may be because it's too cold in your grow area, and this could also be why your growth is slow.
i don't let my room go under 70degrees at night, or above 87 during the day.
you can pretty much let her get as big as you want before flowering... i would wait untill the nodes are staggered.