That's hard to say. You could try it, but it might shock the plant. I would say if you are going to do it, transplant it when it is nearly bone dry, insert it into a new pot with a really light mix, like light warrior or
FFOF cut with a lot of perlite. If you hit the DP with a bunch of seaweed and some b vitamins, some
hygrozyme, and some roots excel/rapid start, you may have something going. Basically you want to prevent shock, get rid of the dead roots, and promote rapid root growth. Otherwise, just wait until next time and consider it a lesson learned. 40 days is a lot of time, and it may just push off the harvest a bit. However, she will grow a ton in 40 days, so you better have the stretch accounted for --- it will probably keep growing nearly until it finishes. The *worst* thing that could happen is that it could freak the hell out, and it could ruin the plant. Sativas are finicky as hell sometimes. Whereas I literally ripped a rooted clone in flower, replanted it, and it recovered in about a week. YMMV.