Yes, she would. Or you forgot all *G regardless class of travel can access lounges ? When an airline doesn't have its own lounge in other countries they always use contract lounge. Other than OZ use KA lounge in HKG, NH use AF lounge also require lounge invite to get in.

She still need to get a OZ boarding pass in HKG right ? Just show the *G card at check in and they will print out the lounge invite for her, although I don't believe OZ checkin open that early, probably only 2 hours before the flight leaves. I also think that the people work at checkin also work at the gate, meaning they won't get to the gate til the checkin close.