LOL.
I am genuinely puzzled how the Protestant insistence that Mary was expecting to sexually consummate her marriage to Joseph squares with their hypothesis that she immediately understood that she was to be the prophesied virgin. It, too, fails the basic logic. Let's say the Isaiah connection was clear to Mary.
-- Mary, you will have a son who will be a great King. It is foretold in Isaiah. You shall remain virgin through it.
-- Impossible: I am already virgin! Explain!
Logical, no?
Every Jewish woman, and even now hope for, as they believe in a future messiah, wished and hoped to be the one to bear the messiah. Mary would certainly be aware of that honor, and hoped for it.
Joseph's reaction I never considered until... oh, i dunno... what time is it? lol! Obviously, his behavior only makes sense if he draws the same [normative] conclusion. And why wouldn't he?
With the benefit of hindsight, we can look back and say, "Of course she was overshadowed by the Holy Spirit! How else would God become incarnate?", but I seriously doubt this was even thinkable back then.