Hmm, yes, that child conceiving is a bit confusing. Skywise had a child with a Go-back without recognizing her (right?) so it would make sense Kahvi can do it too, they gave up on recognizing a long time, before they called themselves Go-Backs.
I never actually read the comics about Kahvi (again Netherlands suck) but I think Kahvi lost the sense of reality there a bit. She knows how crazy Cutter is about his family, he would never have a cub with her willingly (not after going in wrapstuff because he can't life without his family) and I don't think rape is part of the Elfquest world.
So all in all, I don't think anything would have happened if Kahvi actually took the right cocoon.