Courtesan maintained by Lady Gallorett
Going by the english-friendly name "Faye" in London, Feiyan is a woman in her early twenties. She was born in the port city of Canton.
Originally an employee of an unnamed high-class opium den that offered additional "services", she is now a courtesan maintained by Lady Gallorett since September 21, 1874. As off September 1875, she has been paid in advance by Lady Gallorett for the next 5 years.
Furthermore, Lady Gallorett has had the madam of the opium den cut out of any share of the income of Miss Faye, and made sure that any money she sends to her family goes directly to them via Lord Falkland's man in china.