I know this is an old thread from 2009, but still
When my grandma died, after 48 years of marriage (that we all know wasn't always happy), two children and three grandchildren... my grandpa had his cleaning lady move in with him before the week was over. That... was a little bit too quick for the rest of us. Not even waiting until after the funeral. Or maybe the end of the year (granny died around thanksgiving) or... well, anything longer than five days. Shall I say that Christmas was kind of strange? With a "new" grandma around, holding hands and kissing, while grandma hadn't even been burried yet?
They did stay together until my grandfather passed in 2006 and yes, she was of tremendous help especially taking care of him in the last few weeks when he was in the hospital and everybody else had to go to work. But it made things very difficult for everybody. We really tried to respect his choices and we of course know that (adult) children shouldn't meddle in their parent's love live but I think some part of us never "forgave" him and her being there never felt "natural". She broke ties with us right after my grandpa had passed. Without going into much detail, the whole thing left a very bitter aftertaste for all of us.
It might even have been different if it had been someone else. Someone he'd just met by chance. Someone that hadn't been in his life for 10+ years. Someone closer to his age. Someone who didn't move in with him within three hours. Someone with a little more compassion/empathy for the rest of the family. I really don't know.
My FIL passed away 6 years ago.
We really hope my MIL, who is only 60, will eventually open her heart for someone else. For her sake. She doesn't do well alone, she really needs a companion by her side. It's a hole that her children are unable (and yes, somewhat unwilling) to fill. Her sons can't be her partner and as much as they (we) like to help her as much as we can, there are limits.
She is very Catholic, which likely doesn't help in this case. But I really hope that there is someone out there she will be able to spend the rest of her life with who can provide her with what is currently missing in her life. I really believe it would be good for her.
But obviously, she is still grieving. Maybe she is somewhat punishing herself because she thinks it's her fault (long story, of course it's not but there is reason why she could feel that way). Sometimes it seems that she actively makes sure she will never be happy again, as if it's an active choice to make sure she is as miserable as possible. But I really hope she finds someone and falls head over heals in love with him. My FIL wouldn't have wanted her to be unhappy.