Except that she couldn't have been (absent the Immaculate Conception), because the Sacrament of Baptism wasn't instituted yet. Children (even Jewish children) aren't born in the state of grace, because of original sin.
Where is the logic in this comment?
First of all, Mary was not a child when she conceived Jesus. She was, by definition, a woman since she was capable of conceiving.
Second, baptism does not infuse grace into an infant.
Third, Mary didn't need to be born in a state of gace, she simply needed to be "sanctified" at the moment of conception. That is what the angel declared. It's very simple when you eliminate the unnecessary additions.