I have a Singer that had metal gears in it and I stripped them out (after thirty years of use -- I paid $86 for it used in 1976). My repair guy said the same thing about the cost and my husband insisted that we have it fixed rather than buy a new one. The new gears are plastic... not metal... and the darn thing is so loud that I can't use it.
I have since bought several machines but the Singer in her cabinet is now a night stand. Hubby still counts it in the "machine count" when he is telling folks how many machines I have.
Your niece should probably look for an inexpensive starter machine. You want her first experience to be a pleasant one that will make her want to sew. Janome has several that are good machines.