Was Aisha mature when she married the Prophet?
In a Nutshell:
The answer is yes, most definitely. It was not unusual historically for women living in environments closer to the equator to reach maturity earlier. This still happens in many parts of the world including parts of the USA. From a historical and traditional perspective, A'isha (ra) was biologically and mentally mature for marriage, the Prophet (saw) not consummating the marriage until she had reached puberty - deemed a young adult in his society.