A friend of mine believes that Mary did not have free will as other humans have. Therefore, she had no choice but to say yes to the angel at the Annunciation. This friend believes that God, who is all-knowing, knew that Mary was going to say yes and thus she was not about to say no after God had created her immaculate in her conception.
Your friend is wrong on one count and right on another. God is indeed all-knowing, but why should God’s foreknowledge of what Mary would say be any different from God’s foreknowledge of your decisions or my decisions?
Your friend is assuming that God is limited by time the way that we humans are. You are more present to me than Julius Caesar or Florence Nightingale because you are alive and they are not.
Human beings can only live sequentially; that is a limitation that God does not share. You, I, Julius Caesar and Florence Nightingale are all equally present to God. The term foreknowledge as applied to God is not very helpful because it presumes that God lives, as we do, sequentially.
If you took your friend’s position to an extreme, wouldn’t God’s foreknowledge about Adolf Hitler and Mother Teresa of Calcutta make God equally responsible for their vastly different actions? If God is not responsible for their personal decisions, why should God have toyed with Mary’s freedom at her Annunciation?
Human freedom is very real and can produce very different results. God’s knowledge does not cancel out human freedom—for good or for ill. God freely created everything that exists. Part of being made in God’s image is that we have a limited but very real freedom, which we need to use wisely and generously.
Mary can inspire us to grow as disciples. The generosity she showed at the Annunciation can help in that process.