i would pick a round that will suite your hunting area and needs.my fiaancea's two little brothers ( who are 13 at the time of shooting it ) shot my browning medallion chabered in 30-06sprg using 165gr. loads.

i would go with maybe the 260rem 7mm-08rem 6.5X55 sweede. the 308win would be another fine choice but in a light gun might just kick more than she would want.
plus if you already own a 30-06sprg why get your wife a 30 cal. i would get something differant so you will have two differant calibers to shoot yourself.