Since I send every female shooter I know to Pax's site (Cornered Cat), I recommend you heed her advice about the AR15. And if she want's to plink for the fun only, the S&W MP 15-22 is a really nice, light-weight plinker that will have similar controls and accepts foregrips, etc.
(P.S., I'm left-handed and have no issues with the 15-22 or any AR15 with a deflector. Without a deflector, some AR's fling brass just past my right ear, which is a little disconcerting at times. Of course, there's always a LH Stag