How did Mary know?

Blessed Virgin Mary
I am the handmaid of the Lord

Each time I pray the joyous mysteries, I am always at a loss at the first one – The Annunciation. Mary is approached by the Angel Gabriel and is told that God has chosen her to bear His Son into the world. How could Mary know that the angel was truly from God? We are told that Mary was without sin. Eve was conceived without sin. Eve was approached by the serpent, a disguise of the devil, and didn’t know that the one who approached her was not truthful. How could Mary know? Experience perhaps? Gabriel did announce himself; he told Mary who he was and from where he came. The serpent just began by asking questions of Eve. Could Mary’s experiences as a child, in her time in the Temple, in her training in her faith, in her hearing of the Word of God so enlighten Mary’s mind that she could discern truth from untruth? Did Mary ever wonder after the angel left whether what she thought she experienced was real? Is that one of the reasons Mary went to visit Elizabeth? To test the truth of what she believed had happened to her?

Lots to ponder.