I'm pretty certain that it should work just as well for veneered. The thing you're trying to protect is actually the finish. Any finish coating is pretty thin and oil, even polymerised oil with a dryer added (as I assume the Chestnut oil to be, perhaps Terry could comment?) won't take too kindly to abrasives or harsh alkalines. Lye or caustic soda (an alkali) is used to strip oil-based finishes such as varnish so I have assumed that most kitchen cleaners, also predominently alkali, would have the same effect, albeit in a much less aggressive way. The advice I give to worktop customers (in a snappily titled little brochure, "How to Care for Your New Work Top") is based on what I was given by a worktop fabricator long ago. That leaflet comes with a small bottle of oil, a pair of disposable gloves, a small grey Scotchbrite pad and some lint-free cotton cloth. - as well as my business card encapsulated in plastic. It pays to advertise. Maybe you need to give her the kit as well?
Scrit