Double swing thru the strike zone

[hawk65]

NFHS, last game of the season, no playoff issues for either team. Score is mounting and team A eventually wins 19-2. Late in the game, batter for A decides to experiment/hot dog/accept a dare or whatever. Batting left-handed, just as the ball leaves the pitcher's hand, she swings while stepping forward in the batter's box like a slap-hitter. She is intentionally swinging very early with no intent to hit the ball at this point. She completes her swing, releases her left hand, continues the swing with her right hand, reaches back with her left hand and grabs the swinging bat behind her with her left hand and continues swinging with her left hand in a second swing thru the strike zone. She hits the pitch on the ground in a slap-hit manner and gets an infield hit. Lots of "oohs" and "aahs" and whooping from teammates and fans. Impressive, but is it legal? If not, what rule do you cite? And if she misses the second time, do you call two strikes -- either by rule or playing along with her hot-dogging?