Sandblasting the metal is the only way to get the impurities out before powdercoating. Sandpaper will introduce more carbide and emery into the surface of the rim, plus it will take forever to get down to raw metal, which is what the powdercoat epoxy bonds to when cured.. if you want to get your money's worth, you can't half-ass your prep work.

If she can't afford to sandblast & powder coat, I suppose she could hand-sand them and paint them...but again, it sounds like she'll need a hell of a lot supervision to ensure a quality finished product.

First off, she needs to learn the proper way to wash a car IMO. h: