Princess Alexandra is a character in the game Warlock of Lust. She is chosen by her mother - queen Augusta to replace you on the imperial throne. However she is not aware of this as she is still at the convent, she was sent as a child for education. You will learn about her whereabouts from the queen during a quest Fallen queen. After traveling to the convent she will not recognize you and will remain indifferent to you.
To proceed with her conversion, you must raise her Lust during a quest line "Seeds of corruption".