So was my wife's grandmother, well into her eithies. She did get a little thinner after she got senile (probably mini strokes , my Father in law had those too, but was always thin like his father, of course at the end he was skeletal) My grandmother wasn't thin, well my paternal one was but she died in her 50s from cancer, but she died in her late 60s, from cancer. Needless to say, I get the old bowel inspected pretty frequently. (Dad had colon cancer too, but they caught it soon enough and he lived for about 15 years after that)
Yep, we’ve got to keep watching out for stuff that hit our families, which is cancer for mine. Good idea to keep watching that bowel, and colon. Your wife’s grandmother probably got thinner because she ate so little. They probably had to fight to get her to eat. That isn’t life. It is existing.
Take care.