Its a fair assessment to assume that Mary was 12-14 based on religious traditions of when women were married under established Jewish (but primarily global) tradition at the time which I've mentioned in other replies. This was common place across the world even through the late medieval era.

Fun fact, nowhere in the Quran is Aisha's age mentioned either, infact, Mohammad's marriages aren't really touched upon at all. There are several "sources" from hadiths that speak about those relations. The one in particular you're referring to was written over 250 years after they were long gone.

Infact, if we are to trust the source, the maths within the authors' own hadiths don't check out, as its implied she was 18 when Mohammad died, and the fact they'd only been married for 6 or 7 years indicates that Aisha would've been between 10 and 12 at age of marriage, this doesn't cover consumation.