Continence is my thing...
I second everything that's been said - get GP involved.
Continence is one of these insidious things which can destroy lives. A third of women who leak also have depression, it's associated with heart disease (ever tried zumba with a leaky bladder? I did, wasn't pretty) and in the elderly, there's a risk of hip fractures in people who can't stay in bed all night, get up for a pee, slip and...
So, check no UTI, check no prolapse, see if there's medication which can help, and whether she will be eligible for free pads or benefits to help with the extra washing.
Also - have a look at these guys. Absorbant, washable pants. The stuff is lovely, comfy, discreet and it works - I'm not associated in any way with them other than heartily approving their stuff broby
Pelvic floor exercises will improve most cases of continence - I've got a blurb on my website (find it via my profile, don't want to fall short of advertising rules) only, in the elderly it's usually a bit more complicated than simple new-mum-muscle-weakness.
PM me if you've got specific questions - happy to help. Not just your elderlies, either.