If your wife knows nuts about cameras, get the NEX. It's small and light and very "newbie friendly". The GF2 uses a slightly smaller sensor but is a m4/3 camera with more dslr-like features and more lenses. But a NEX is more "non photographer wife friendly" because the interface is very much like a point-and-shoot. But it does have the APS-c sensor found in the D90 so you can get great shots (got some good ones at the Iron Maiden concert).
Nex5 has an exclusive gold color - NEX3 is a bit bigger but has Pink and Red and is a bit cheaper too.