Well, let us hope that we'll get an answer on this question in the add-on.
Larian already said that "Soon they’ll recognize that many of the characters they met in the main game aren’t who they pretended to be."
Maybe Sassan is one of them. Maybe she is evil and is going to destroy your battletower. Maybe that explains why she has a 'neutral' opinion in the trading screen.
"...and the answers to many questions in the Divinity universe revealed."
