IBgard (time release peppermint basically) helps me the most with constipation. I also take CBD which helps too, but more for the diarhea.
The other thing that helps me a lot is to do a self bowel massage. this can get painful though, but it has a high success rate for instigating movement in the bowels. Basically I lay on my back and with my hand just push in on the gut on the left side and feel the large intestines and then I push in and put pressure on em. and I work my self down the bowel until I am right around the bladder, where you have to push deep. If you did it right, you will be somewhat exhausted.
The reason this helps is the peristaltic reflex reacts to pressure in the bowel and pushes stuff down (normally this is when it expands with stuff). so you are basically activating the peristaltic reflex.
not sure if your 75 year old mom can do that, but she can try. the first time I did it was rather painful, but after doing it for a while, the sensitivity is less.