Is there any reason she can't leave the machine set up and just make a nice cover for it? If he won't pay the money for a lift for her he probably won't take the time to make one for her either.
I can think of a bunch of ways to do it. Is her machine on a hinged platform or does it need to lift straight up and down? Old Singer cabinets used a spring loaded lift assist. They're adjustable so they can be made to take most of the load. If that's not an option then a pulley and counterweight to balance the weight of the machine could be rigged.
Some old treadle cabinets were pretty ingenious. When you lift the lid the machine is raised automatically. A system like that would give her a lot more leverage to raise the machine.
Hooking up a motor gets more complex. My gut feeling is a sewing machine motor is too small.
Rodney