From What I read many years ago, there were two version why Kuan
Yin becomes a girl.. firstly it is because Kuan Yin was very
compassionate that are commonly found in a women character ..
secondly which is more to be accurate is that Wu Zhe Tian wanted to
be a goddess herself and declared that Kuan Yin was a woman
instead. She also order all Kuan YIn status are to be craved as a
woman figure ...