Before trying all the lubricating ideas mentioned above, check the derailleurs. Try moving them by hand to see how forceful the springs are. Try moving the derailleurs of other bikes for reference. If your wife's derailleurs have unusually strong springs, that may be the source of your problem. I don't have a fix for that. Anyone else? Change springs?
I switched front derailleurs recently. My old one shifted easily with twist shifters. The new one requires some muscle. I'm a rock climber, so I consider it part of my training.
