Why did she dismantle the 3018 router in the first place? Because it didn't work well? Or just because she likes tinkering with things? (A lot of us here can relate to that). It sounds like your simplest route towards a working desktop router would be to put it back together, maybe with different electronics, since that's usually their weakest feature.

Are those cheap SBR rails supported along their length? The unsupported ones are basically worthless, which might be why they were so cheap.

It sounds like your daughter might be looking for a manual machine, rather than a CNC, Are you and her really on the same page here? Did she ask Santa for a Bridgeport, but you showed her your pile of junk?