Ordinarily, I don't touch anything with the i-word, but you managed to make it make sense. Darn but meimei needs a date. She needs to dance somewhere where people can see her. Then she wouldn't think no one but Simon would give her the time of day.
These thoughts match the face in the ceiling, the girl in the closing sequence of Serenity.
They found the hardwired origin of the incest taboo. Regardless of genetic proximity or lack thereof, people are grossed out at the thought of romantic relations between sibs with whom they grew up as children, even adopted sibs.