Hello
So with the jiffy pellet size...eventually you're going to see roots poking out of it and when you do transplant right away so the roots don't get much light, otherwise I'd say let her go another 3 days max before transplanting. I usually go into a solo cup size first, let it get about 6 inches tall and several sets of leaves before putting into the final container. Maybe just do a 1-3 gallon pot if it's gonna live in the window, that's big enough to get many J's.
Id use a fabric pot if i were you? Because they don't stay soaking wet for too long and it air prunes the roots. Smart pots are a good brand but any off brand works just as nice.
Good luck with the grow, cheers to home grown J's.🌱💚