There is a strange thing about old people, the people in their 80, 90, that they are happier than the young folks.
They don't remember past predicaments unless they work at it. The generation question is a wt problem a real serious one*, but not theirs. If your mother is a natural 80 year old, and not in pain, having successfully reproduced, and have gotten to that stage, should make her content.
The really scary, hidden thought for them is, that if the wt survival promise is wrong, the resurrection, immortal souls promise might be wrong too, so: do not bring the subject up, but concentrate the conversations on the good of life itself, the offspring. the spring.
*I have seen only one attempt to seriously debate a glaring inconsistency of the current wt proposition.