Info needed on a plant that is on its third grow

I have acquired a plant named sheeba. She is on her third grow. it was givin to me by someone who moved out of state and couldnt keep her. I am wondering if its ok to put her in the flowering stage now, she was harvested on 4/20 . and put back into vegetative stage. 18/6 light. she is approximately 20 inches high . and full of new leaves. like 3 or 4 nodes. any info is needed. i am a first time grower. i have read that i can put her into flowering mode sooner than a first time plant. again, this is her third grow, HELP

You can flower at any "time". You could flower from seed. It all depends on your space and how tall of a plant you want. Is it sativa dominant? Sativa can stretch up to 3 x whatever height they are when you flip to 12/12. Mainly indica don't gain much height. 50-100% maybe.