Most walker fitting happens in daylight, with someone standing close by. The night trip is different. The light is low, she is half awake, and the space she needs to turn is where a walker tends to catch. Measure the route the way she will walk it at night.
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.
Walk the trip with the walker she uses
Use the walker she actually has, not a spare. Start at the edge of the bed, then walk the full route: bed to walker, through the bedroom door, along the hall, through the bathroom door, the turn at the toilet, and back. Mark each turn point with painter's tape on the floor so you can see where the walker has to go.
Walk it slowly, the way she would at 3am. Notice where your own hip or elbow would brush a frame, a corner, or a doorstop.
Measure the narrow points
Measure the clear opening at each door on the route. Measure the narrowest spot in the hall, including anything that sticks out, such as a table, a radiator, or a laundry basket that lives there. Then measure the open floor where she turns at the toilet and the sink. Write each number down with the place it belongs to.
Compare each opening to the walker's width with room to spare. Judge the margin by walking the route, not by eye alone. If the walker has to be lifted or angled to pass a point, that point is a problem even if it technically fits.
Check the bathroom door
If the door swings into the path, the walker has less room to turn. Check which way it swings and whether it can be held open or fixed in place. A contractor or an occupational therapist can tell you whether a change is worth making. Do not take the door off or change its hinges on your own without asking.
Set the height and check the parts
Set the walker height with her standing in the shoes she wears at night, arms relaxed at her sides. Check that she can lift the walker over the threshold, and that any basket or tray does not hang into the path. Check the brakes and the feet, and whether they catch on rugs along the route.
What to write down
Write the narrowest opening on the route and its width, the turn space at the toilet, the height setting, and the one place where the walker had to be angled. Note anything you moved to make it fit. If you are unsure whether this walker is the right one for her, her doctor or therapist is the right person to ask. The sources page lists the public references behind this desk's advice.