right before a punch, she steps back and exposes one part of her body. left nipple = up + left punch, right nipple = up + right punch, left buttcheek = normal left punch, right buttcheek = normal right punch. Then, when she's stunned, it takes one normal left or right punch to extend the stun and make her vulnerable to everything.
If you played Punch-Out, it's similar to King Hippo