At 3am the question is not whether a bedside urinal works in general. The question is whether your mother can use this one, from this bed, without standing up on the route you are trying to keep her off. Judge it on four points before you buy it or set it on the nightstand.
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Check the grip first
Ask her to hold the empty unit the way she would in the dark. Can she close her hand around it without looking? Does the shape let her keep her wrist straight? A unit she cannot hold steady at night ends up on the sheet, so this test comes first.
Check the bed height against her seat
She should be able to sit on the bed edge with both feet flat and reach the unit from that seated spot without twisting or leaning off the mattress. Test it at night-time bed height, not in a daytime chair. If the reach needs a lean, the unit is in the wrong place or the wrong shape for her bed.
Check the empty and the tip
Write down who empties it, where, how often, and whether that person can do it without walking the whole night route in the dark. Check that the lid seals and that the unit stands upright on the nightstand or floor when it is half full. A tip at 3am is another fall waiting to happen.
Check the plan with the physician
Whether a bedside urinal is the right answer for her is a clinical question. Ask her physician whether it fits her condition, her balance, and how often she gets up at night, and bring your night log to that conversation. The device does not replace the physician's view of the night trip.
Write down what you tested
Note the grip result, the reach from the bed edge, the tip test, who empties it and how, and what the physician said. Keep that page with the night log. When you look at a second unit, run it through the same four checks rather than comparing the packaging.