@SovietWeeb My thoughts were more along the lines of her being the child's twin, and due to political reasons as yet unexplained she was taken by her foster father. This could explain why he thought it was fate that she ended up in the palace, both because he took her from there and because he was once a doctor there. She's probably not the twin, though, as there's little to hint at such a plot twist aside from the fact that she is probably around the age of 17 years right now.
Was her age ever confirmed, btw? I only know that she is younger than 20, and that she is clearly quite young, but she seems older than Rishuu who is 14. At the very least, Maomao could be 18 or 19 and still be worried about the sake ban towards those younger than 20.