I'd guess that it probably won't happen very often. Good for her that she has the heart to go after a lion, but if it were me, I'd make sure she didn't go solo after a healthy one. A lion that size wouldn't have a lot of trouble killing a dog. Dogs that have that much heart and drive are the real deal and I'd save her for hunting in a pack where the other dogs can distract a dangerous animal and bring it to bay without trying to do the killing themselves.
Anyone who says that Airedales are for show haven't seen the real McCoy, I imagine. Your dog sure is the real deal.