I live where it's a bit hilly. I simply replaced my front 44 ring with a 36 on my 3 speed c/b Nexus equipped cruiser.

Those things take the same rear sprocket as any coaster brake bike so you should be able to get a 22 or a 23 tooth rear, which is another way to lower the gearing.

Your wife may have to use higher rpm while cruising on flat ground but that's good practice anyway.