I would tend to agree with that. I think that the idea that Mary was instantly aware of her fulfilling the prophecy in Isaiah is an interesting hypothesis that has no scriptural support: the Luke's chapter does describe her mental state, and it describes it as confusion rather than an "aha moment". Later, she is described not quite understanding her Son as He stays in the Temple. The Church does not call this ideas wrong, but it is but a hypothesis, and it seems at odds at least with the above episodes.
John Paul II indicated that there was a Messianic fervor at this time. It is NOT a stretch to think Mary fully understood that she was chosen to give birth to the Messiah. Whether or not she realized that He was also God, I doubt. Jewish understanding never seems to have caught on to the fact that the Messiah would be God.