I think you're exactly right about this. However, that would put Mary in even more of a jam. :) If she never had any intention on having conjugal relations with a man, then she would be guilty of dishonoring her parents. "Wifely" speaking, she would be damaged goods, and would have been honor bound to inform her parents that she was not suitable to be given away in marriage.
I believe that your Tradition says that Joseph was a much older man (I have no opinion). If so, I doubt he would be interested in marrying any 16-year-old mostly for her sparkling conversation. Had the angel never appeared to Joseph, which Mary could not possibly have known would happen, then I think Joseph would have rightly felt ripped off. :)
Unless, as was the case, her parents Joachim and Anna intended the marriage to be a custodial marriage.