Of course Callista wants to save everyone, not just Kane... She's not a fucking psychopath lmao. Also, Kane isn't even her only child. She has a responsibility to not only help Kane, but Seth, and Olivia, and other people who are important to her as well like Cola and Veronica.What you write is logical, but if a mother has anything more important than her son, there is a problem,
because what's the point of saving humanity if in the meantime your son dies or becomes a degenerate servant, someone else's toy.
And, Kane is going to die anyways... because humanity is dying... she is literally giving him a chance to save himself AND save everyone. Not only that, but she seems to have a backup plan or two anyways in case Kane is a complete failure.