My mother-in-law needs help pulling up her adult diaper. Is there a product to help her to be able to pull them up herself?

Missguineapig: Perhaps she should be using the type with side velcro tabs.

I'm surprised they didn't send her home with a "grabber" and a sock "pull 'er upper". So she doesn't have to bend over. I have several that my husband used, and now I use them. Getting older is no fun, but better than the alternative. Hopefully, with Physical therapy, she will recover soon. My prayers are with you both.

Depending on her level of incontinence she may do better with Briefs (the tab style that open at the sides) or she may be just fine using one of the extra coverage pads rather than a pull up, I'll link two from Tena

https://www.tena.us/day-plus-pads/6261862618,en_US,pd.html

https://www.tena.us/TENA-ProSkin-3XL-Night-Pads/5439200,en_US,pd.html

Do a search for Wings Pants Dressing Tool.
I just watched a video on this and it seems very easy to use. Should work with disposable underwear, regular pants even skirts.
The site that I saw it on was arthritissupplies.com