These solid brass hose splitters are sturdy and last forever, but MrsWD has a ot of trouble turning them off and on. She needs some kind of tool to give her better purchase and/or better leverage. I've seen tools that are essentially a cylinder with a slot cut in it at the end of a screwdriver handle. Something like that would work. I don't know what to call the tool or where to find one.
If I had a milling machine I'd cut a slot in a 1/2" nut driver and be done with it.