The Kel-Tec Sub 2000 have been hard to find lately and I'd love to get a 9mm for my wife as well. When I find the Sub 2000's they have been going for far more money than I'm willng to pay for a plinking carbine for my wife. I don't know how the brass ejects on the Kel-Tec SU16 but they can be had for less than $400 still, and it looks like a handy little rifle.
I'd buy one for myself as my wife doesn't need it. She keeps her GP100 .357 in the nighstand, and her Colt AR15 in the closet, and she packs a PX4 SC 9mm for her CCW.