Pretty sure that person we saw in the beginning might have been Suirei. Could she be posing as one of the newly acquired eunuchs to get access to the rear palace again? There were rumors of a beautiful eunuch this episode, it might be her.

Also, this episode pretty much confirms (in my mind) that Shisui is most likely Loulan. My theory of the case:

• Loulan is extremely private, not really leaving her pavilion unless she has to. Also, hardly talks at all in public
• Shisui is oddly knowledgeable about tons of stuff that a normal servant girl wouldn't be (Maomao even compared her to Gyokuyou this episode)
• Shisui deftly avoided coming face to face with Lishu this episode, perhaps she would be too easily recognized
• Mamao commented in the ghost stories episode about how good of an actress Shisui is
• This episode they commented on how different her body looks when she is undressed

There is quite a tangled web brewing here. Loulan's father tried to set up an environment where Jinshi would get killed. Similarly, Suirei was part of a plot to kill Jinshi in the first season. They might be connected in some way. Also, the way things get connected in this series, I wouldn't be shocked if the fact that the girls are using scented oils in their massages ties back in to the attempted abortion drugs earlier this season that also relied on scented oils and perfumes.