I've heard that St Pio said that you will know it's truly Our Blessed Mother if her feet are showing. They, after all, will be what stomps the head of the snake. I've also heard that the feet are covered or unseen at Medjugorje. It's always seemed to me that she's way too chatty there as well -- not to mention the fact that her alleged messages are at times at odds with the traditional teachings of the Church, etc.