to echo frappée I would use grief stricken as it is a common way to say suffering due to a loss

or suffering (from) the blow to her (family) stock

I think it's important here not to lose the meaning of 'descendence' as I think the author wants to portray the fact the woman is not only grieving for the loss of that individual person (her grandson) but also, being an older person herself, the fact that she will have one less descendant-this is a reminder of her own mortality. The whole passage is about her reflecting on life and death, it's her questioning how someone is brought into the world and taken from it and if and how the two are connected. To not translate descendence or to translate it generally with 'family' is to lose this depth of philosophical and emotional reflection IMO. The writer would not have chosen such an expression if they just wanted to say 'loss' for someone who has died.