On that, I agree. It is over the top, and a Catholic Christian does not have to believe that. But the fact that Mary did not understand how was it possible for her to have a child (luke 1:34) is Bibilical evidence that for one reason or another she was under some vows.
WRONG. The fact that Mary did not understand how was it possible for her to have a child (luke 1:34) was because she did not yet have sex, which she states.
All it does is confirm her virginity at the time of conception.
It in no way gives any indication of her future plans, your wishful thinking notwithstanding.