Once a Lunarian princess, she was banished to the region of Earth that would eventually become Gensokyo for creating the Hourai Elixir with Eirin Yagokoro.
She is currently the princess of the Eientei mansion.
She has existed for at least 1300 years, although Zun once drunkenly remarked that she was hundreds of millions years old. So yes officer, she was old enough.
This tag implicates touhou (learn more).