I worked on a lady friends one, old, solid, chromoly.
Hey, I bet your headset is loose if it's the same bike! Kidding.

Being old, check the bearing grease in the hubs and bb, I imagine the bb has not been replaced = IF it wasn't run loose, pack it NOW with the grease.
You may be able to keep it running for a while with new balls and grease.

If loose or fouled grease\pitted balls, it will erode fast -then you have to buy a cartridge bb 25-40$ to keep riding.

I kinda like the idea of keeping the loose ball bb going, a little work, balls\grease cost little.
Check the tires, brake pads and cables for decoposition of the rubber and plastics.
Replace whats needed. Any cables with corrosion need replacing as they wont slip smoothly in the cable housing.

Have fun, all you need, until you outride it. Then keep it for a commuter and shop for a fancy-pants bike.