20 years ago, she would have been one miserable sailor, as the A1 threw a lot of brass down my shirt collar back in my infantry days (still have the hot casing scars to prove it). Since the advent of the A2, of course, that's all changed: there is very little a left-handed firer need know, save for the basic manual of arms.
Keep in mind that southpaws (myself included) have been adapting to a right-handed world since childhood, so many times the right-centric design features of a rifle like the AR are going to be almost completely overlooked. We might ponder why a certain control or switch was placed where it was, but our only real interest lies in learning how to employ it effectively. I don't think of the AR as a right-handed rifle; I simply think of it as a rifle that put the selector switch in a rather strange place for me to activate it. :) Everything else is pretty straightforward.
Hot gas and spent cartriges? Nah, not to worry. Just throw the rifle on her left shoulder, and instruct as usual. She'll change mags and such a bit differently than you, but the end result will be the same: rounds on target and that hard-to-conceal look of satisfaction.
Chief