Personal hygiene?

Talcum powder with lavender worked with my mom, as did baby powder. I also kept her nighties in dresser drawers lined with scented paper. My mom liked lavender talcum because her own mom used it when she was a child and she associated the fragrance with a feeling of fondness and the security of family life.

Here is an article

https://www.agingcare.com/articles/old-person-smell-174839.htm

You do not need to bathe Mom everyday. It actually will dry out the skin. As do deoderant soaps. In NHs and ALs, they bathe residents maybe 3x a week. My Mom had problems with underarm smell. Traditional deodorants broke her out. I found that Arm and Hammer unscented didn't. On the days I didn't give her a shower, I washed her underarms befor putting on deoderate.

If you are cleaning Mom up well, that should do. I found I liked Huggies. No alchohol, bigger than women's wipes and thicker.

Soaps, tons of liquid soaps with moisturizers. No ivory products I find they dry skin out. Same with Dove. My skin itched. I have been using Oil of Olay. I find I don't itch and my skin is not as dry. With Dove and Ivory, never tried the liquid. May be different.

I like the idea of exfoliating to get the dead skin sells off.

I think cornstarch intensifies body odor.

Do you ever use any type of exfoliation? I would use one weekly to help remove dead cells and see if that doesn't help. I would also try unscented baby body wash, it is gentler.

I agree about the deodorant soap. I'd be very wary of that. That can be very strong and irritating to sensitive skin. I'd discuss it with her doctor to see if she has an infection. Also, I've noticed that sometimes you can get an odor in your mind/nose and it's hangs around, even when the actual odor leaves. I know it sounds odd, but, I've known that to happen to multiple people, including myself.

I wouldn't use strong soap on her elderly skin, which can be quite fragile, and I'd skip the cornstarch in favour of moisturizer. It could be from the meds she is taking or an underlying health condition, it could also be "old people smell"....
https://www.agingcare.com/articles/old-person-smell-174839.htm
- no doubt you have become hypersensitive to it as well.