Kinda, yes.
Maomao is the only person at the party who doesn't know that Jinshi is the (presumed) brother of the Emperor due to how narrow her viewpoint has been the last two years. She has been given all the hints, but missed the obvious connection. The Emperor was invited but declined to go. But this 'Koumen' got sent in his stead.
What she does suspect is that the brother of the Emperor is actually Ah Duo's son and the son of the Emperor (i.e. the Crown Prince), but she hasn't made the connection that the reason Jinshi is placed where he in in the Inner Palace is because he's the Emperor's brother. She really just thinks Jinshi is a very attractive eunuch from a good family.
Publicly, the Emperor's brother is assumed to be very insular and makes very few appearances.
Loulan's father is trying to get the Emperor's brother all horny during a very rare outing.
It just doesn't work on a girl who grew up in the Pleasure District and is already very used to eating aphrodisiacs both as a matter of course and from her hobby as an apothecary, haha.
The same thing happened when Maomao made the chocolate fondue bread aphrodisiacs, and all of the younger servants got very hot and bothered but thankfully didn't go all the way with each other, they just passed out the same way that Basen just did.