Okay. You uppot when or before your plant gets root bound. As she's so small on top.. so, in reality top is like a mirror to bottom. You should have left her. She would of took hold, (the roots) and spread out, and you'd of seen rapid growth (a root ball)
But now, your gonna have to wait until the roots grow more and she'll take off.
There's not much you can do now but give her love.
And do a test. Get a stick and push it through soil(, away from plant) your sub might be too compact. This would only have a light impact though. But you should have left until she developed a little more. Look when I uppot around day 10-14. A bit before that size is when you should uppot.