When the angel said Ave Maria

There are many reasons for the familiarity shown by the angel toward Mary in the way he greeted her. 

'Ave' is how people greeted a friend or relative arriving at their doorstep after a journey. This is what Mary said to Elizabeth (which caused John to leap in her womb). Thus the angel used a familiar expression with Mary, who was troubled at first because of her humility: How is it that (to foreshadow Elizabeth's words) an angel of light should use familiar language with me?  

Mary was wise enough to gently but firmly test whether this was a 'familiar spirit,' with a prudence beyond Eve’s, who failed to test the serpent's spirit. Mary said: "How shall this be, since I am a [consecrated] virgin?" It was not that she was unaware of the facts of life, or ignorant of Micah's prophecy, on account of which all the consecrated virgins in Israel hoped that they might be one day be the mother of the Messiah. Mary was so humble that she never presumed to be the elected virgin.

By hearing the dignified words of the angel, praising as he did the Ruah Khodesh (the Holy Spirit) in explicit terms so rarely seen in the Hebrew scriptures, she must have known that this was an angel of light, and not the opposite. Because of his very high mission, the angel knew from the outset that he had to be prepared to answer the holy questions of the woman called to be the queen of heaven—his own queen! For this reason he bowed to her, as one would bow to a princess God destined to be queen. You wouldn't yet say "your majesty," but you certainly would say "your royal highness" and bow as if she was your majesty…

If I were that angel, I would be trembling. And I should imagine he utterly prostrated himself afterwards when Mary said: "Be it done to me…" and conceived the Son of God, for then she became the exalted and perfect tabernacle of the Most High

Contributed by Gary Knight, a Canadian reader of A Moment with Mary, October 2019