Wing walking has to be one of the most physically and mentally challenging aviation feats there is. There must be perfect coordination between pilot and wing walker. The wing walker must be physically strong enough to withstand the 80-knot or so slipstream while moving around on the aircraft, waving, dangling legs, and hanging upside down from struts.
Not only does the wing walker have to do all of that, but she does it while the pilot flies a full aerobatic routine. I have enough trouble walking on level ground at times. To walk a wing while it flies an airshow routine is truly an awesome feat.