A plant that size should be fine in a 3 gallon pot, but 5 would be better.
You can still transplant up to the second week of flowering.
If you do transplant her, just use fresh soil and don't give any teas or dry amendments until she has settled into her new home for at least 2 weeks.
If she were in a five gallon much earlier, I would expect her to be 4-5 feet tall by now.
Cheers, Organoman.