My guess is the lever and linkage are gummed up or need a good squirt of oil. The gear for the feed dogs may look like a tuning fork with a square piece of metal riding between the tines. If oil gets dried on the tines the feed dogs won't go through the entire motion. If the feed dog setting knob won't turn to 'UP' it is gummed up underneath. Some isopropyl Alcohol is great for unsticking tight metal parts under a machine ( I don't recommend using it on the paint, even though I have with no bad effects on a 50's or 60's painted machine.) Have her flip the machine back and turn the hand wheel to see how the feed dog mechanism works, and while she has it up, have her oil everything that moves that is metal to metal.