My wife has a real talent for scratching her iPhones and iPads, so sympathies.
The glass on the Sport is pretty hard, and similar to the glass used in high-end Casios meant for outdoor activity usage. And my high-end Casio Pathfinder has a bunch of small and not-so-small scratches after several years of daily use.
Shrug. It happens. Battle scars.
Sapphire will be more difficult to scratch but it will scratch, too.
It's a watch. Watches scratch. Sometimes I think crappy plastic crystals are the way to go: they scratch like crazy but are easy to polish.
I hope your wife feels better about this as the days go on. Enjoy the functionality!