In the bedroom, Trixie acts as the traditional Dom role, and Twilight as the Sub.
Outside the bedroom, Twilight is the head of the household. She is more responsible, a natural leader, and the tree house is under her name. In this way, Twilight is actually the Dom, with the bedroom being a playful exception.
But at the next level, Trixie is actually a god, making her the ultimate dom, with her mortal life being a loser the playful exception.