look, i am going to give you some advice that is from my own experience, first of all
on the lights!! Toss her into flower!! and get ready for that thing to double in size in a week!!
I'm doing my first grow.. I switched to flower b4 I left for a Christmas trip, and when I got back... HOLY SHEEET man, the things more than doubled on me. one was about 10 inches and is now 3 feet tall now 5 1/2 weeks into flower (btw my widow was about same size as yours when i flowered but a little more dense and its now 2ft tall and almost as wide)
also I had one that i threw into veg for 2 weeks, it was about 3 inches tall, i never counted the nodes.. but its now 14 inches tall. it showed no presex obv. way too young right!! and now its one big nasty bud! also what u can do is start a new grow with the lights u have, shorten the time of your next harvest.
or top it/her !! and give it 1 to 2 more weeks