Help with a auto flower in with regular

Hi all i got a problem i didnt think through i put a auto flower in for something abit quicker but didnt think about at the end now its ready but the others have just started flowering, what can i do to flush that 1 plant or shall i just crop it an have a harsh smoke im not sure its a 1st grow. I thought about taking the rockwool cube out off the tray cut roots off around it to get it up off the matting but the obvious problem will it kill it by cutting that much root off my guess is yes,
any help id appreciate or have i just made a dumb mistake