Really, this is amazingly bad planning if they couldn't use the mother. I mean, part of the plan was supposed to be "Get my limbs
back from that horrible woman." We have both genetic reasons to assume and a track record to say the tissue would be compatible. They should have been ready to ice mom within moments after her death, and if it turns out they need a heart along with the limbs, well, only appropriate to remove something the bitch never used in the first place.
So yeah, I really don't get why not her, aside from "incompetence".
@JavelinJoe I don't get you. Receiving a transplant is receiving a transplant--how would it be more traumatic if the source was a different person?