The custom for marriage was around 14. The Tanakh tells us in Isaiah the Messiah's mother would be:
יד לָכֵן יִתֵּן אֲדֹנָי הוּא, לָכֶם--אוֹת: הִנֵּה הָעַלְמָה, הָרָה וְיֹלֶדֶת בֵּן, וְקָרָאת שְׁמוֹ, עִמָּנוּ אֵל.14
Therefore the Lord Himself shall give you a sign: behold, the young woman shall conceive, and bear a son, and shall call his name Immanuel.
Age 14 is a Young Woman.