Cooda - there's also a free bus tour of Singapore (or there was 6 months ago) for transit passengers who have at least 5-6 hours to spare. Just what she wants, I guess, to be stuck in another cramped seat...
Huge, airy, modern, uncrowded, excellent shopping and entertainment - there are a lot worse airports to spend a few hrs...
BTW there's no longer any need to bring vegemite, it's freely available in MAN
God luck - SLF