Products for the night route are sized for an average room and an average person. Your house and your mother are neither. One Saturday with a tape measure, a notebook, and her there to sit on the bed will tell you more than any catalog page.
Local option: New Plan Care gives families in the St. Louis area in-home help so a parent can stay home: companionship, help with bathing and dressing, meals, and overnight care. Call (314) 405-0887.
Measure the bed first, with her on it
Measure the height of the top of the mattress from the floor with her sitting on the edge, feet flat. Note whether she can get her feet flat, and whether she pushes off with her hands. Measure how far the bed edge sits from the nearest wall or nightstand, since that is where her hand goes first when she stands.
Measure the walk, stop by stop
Measure the clear width of the path from the bed edge to the bathroom door at its narrowest point, not at the wide spot by the dresser. Measure the clear width of the bathroom door. Measure the height of any threshold lip she has to step over. Note where the floor changes material or where a rug sits on the path.
Measure the toilet and the approach
Measure the height of the toilet seat from the floor, and the distance from the front of the bowl to the wall behind it. Measure how much room there is beside the toilet for a frame or rail to sit without blocking the door. Note which way the bathroom door swings, because a door that swings into the path can stop a person in the wrong place.
Write it down and bring it to the installer
Put every measurement on one sheet with the room name and the stop number. Mark the narrowest point on the walk. Give the sheet to whoever is quoting the work, and ask them to check each measurement against the product before ordering. Do not accept a fit that was measured for a different house.
If you are starting from scratch and are not sure which products or services are worth looking at, the reading path on this site shows the order to work through the questions.