According to Canonic law, the minimum age for marryage to be valid for girls is fourteen (it can be and usually is higher for the marriage not to be illicit):
Can. 1083 §1. A man before he has completed his sixteenth year of age and a woman before she has completed her fourteenth year of age cannot enter into a valid marriage.
Since Mary gave birth to Jesus at similar age and is important enough to make an example of sort, I guess that tradition of her age at Annunciation may have played a role in forming of this law.
My question: is this role marginal, non-existent, or important? Are there any sources for it?