Hey!
So first things first..
Before switching to flower you need to make sure your plants will fit in your grow space without going into the lights and getting light burn.
Plants normally double or triple in size when they're put into 12/12..
So lets say the tallest they can grow is 1,5 meters tall then I suggest switching them around 50-60cm so they don't get too tall.
Wonder pie is a Indica sativa hybrid so she might not stretch that much but you never know..
Now if you don't have a height limit then whenever you see that she has a nice structure and plenty future bud sites to flower.
Hope this helped, any questions just let me know.
@ me or DM.
Good luck and happy growing!