I would agree with you if Chris were more seriously disabled or if his disabilities were likely to cause premature death, but all ween catastrophizing of Chris's health aside, he's pretty obviously going to survive Barb by at least a decade or two. Why would that be her responsibility?
I would argue that as a parent who knows thier child is "challenged" she
should be making arrangements for their care after they've died.
Barb knows Chris, better then anyone else in the world, she knows he can't handle adult life on his own but I don't think she's made a single plan for Chris after she's gone. Wouldn't a parent who cares want to ensure thier child is looked after once they can no longer watch over them?
I know that if I had a child like Chris (God forbid) I would have already set up plans in case I met my end early by accidental death by making sure he has a responsible guardian lined up, a secure home that paid off or make sure he can get into a group style home so he won't be all alone until his end comes. Plus I'd leave a fair chunk of change to offset any unexpected events that might pop up...say like a house fire for example.
I doubt Barb has done any of these thing and by her record she won't do any. Chris life is hell because she, for what ever reason, decided not to try to help him but to just let him be a man-child for the rest of his life probably because it's easier to humor him then to try to help him grow up.
Chris life is the way it is by 40/60. 40% is his own fault because he is a lazy dumbass but 60% is his parents fault for letting him be that gaint lazy dumbass when they should have done....I dunno, something.
Chris is the perfect storm of fail but in the end he is the one who has to live with that failure even if most of it was someone's else's fault. In 5 or 10 years Barb will be gone and Chris will have wasted what ever piddly amount of money she left behind. He will be all alone, destitute and God knows what else by then. If he thinks life is hell now, well he ain't seen nothing yet.
It's enough to make you cry.