For the effect of “Harpie Lady 3” count only your opponent’s turns. If your opponent’s monster attacks “Harpie Lady 3”, then count that turn as the first of the two turns. (So the monster could not attack again that turn, even if it had the ability to attack more than once, and it could not attack on your opponent’s next turn either.) If “Harpie Lady 3” attacks your opponent’s monster, then that monster cannot attack for your opponent’s next 2 turns.
If “Element Magician” attacks and destroys “Harpie Lady 3” while there is another WIND monster on the field, “Element Magician” cannot attack again that turn.
If you control “Harpie Lady 3” and “Gemini Elf” and your opponent activates “Change of Heart” to gain control of “Gemini Elf”, then attacks your “Harpie Lady 3”, your “Gemini Elf” cannot attack for 2 of your opponent’s turns, even after it returns to your side of the field.