It will help.
I'm 64. Exercised regularly in my 40s - 3 times a week, but then stopped - life got in the way: full-time work and caring for three people. By the time I was 50 was overweight again. No exercise apart from being at work and caring at home.
Widowed 3 yrs ago. On my own. Had given up my career at 58. Went into a depression. Mobility worsened.
Now...some of the problems you mum has are age related. We can't escape that. But...I've started exercising again. Had a shoulder decompression. (Problem caused by moving and handling adult invalid.)
Saw a good physio. She looked at me as a whole - not just the shoulder problem. Gentle exercise and then referred to a class which I attend once a week. Now doing band exercises at home.
At the class - gentle step (my knees are shot - genetic problem), walking on treadmill, elliptical set level, sit to stand with medicine ball, arm weights...
I'm gradually increasing and intend to return to the 'normal' gym. I've already seen the benefit.
At one point, I couldn't get off the couch without using my arms. Now I can stand up whilst holding things. My arm muscles are coming back, thank goodness.
My late husband did weight training most of his adult life. Gave up in his 50s - problem accessing the gym at work and had developed diabetes. (Controlled via injection.) Also turned out that there was a family heart problem he'd inherited.
In his late 50s, took up karate. Stent put in at 63, black belt at 64. Thereafter, trained twice a week and trained youngsters.
Had a triple bypass at 71 (genetic problem I mentioned). Stroke at 73. (Caused by afib as a result of the genetic problem.)
In hospital for 4 months. Men with lesser strokes came out in wheelchairs. DH came out walking, albeit with a stick. He treated his physio like training sessions.
Made it to 82 - heart attack took him during lockdown. He'd had an acute kidney injury (diabetes related) and we couldn't get med help until he needed hospital (because of lockdown). Was taken to hospital. Made it home after a couple of months, but had been taken off some of his heart meds and he died at home.
The point I'm making is that DH had bad luck from a genetic point of view, but all his training paid off. The physio at stroke rehab told me that that was why DH made such a good recovery.
I can't do a damned thing about my knees - patella alta - but I can work round them. I have a lot of catching up to do, but I'm doing it.
You're doing the right thing. Kudos.