Answer:
It is almost impossible for a western girl to become a Geisha. Geisha are only Japanese females, and they begin their training around the age of 16.
There have been two instances that non-Japanese women have been allowed to become Geisha, and that is because they were being near the Geisha as a study, and the Geisha took them under their wing and allowed them to go through the process.
If you would like to become more like a Geisha, take lessons on manners, etiquette, poise, as well as Japanese dance, poetry, conversation skills, and classic Japanese instruments.