Liu Xuelian does indeed hold a grudge against Sisi, though that's how she sees it—it would be more accurate to say there's a past grievance. And it's not actually a grievance between her and Sisi, but rather between the Liu family and the He Family.
Indeed, Liu Xuelian is the granddaughter of Liu Jinyi, the He Family's biggest enemy. Because Liu Xuelian is pretty and sweet-talking, she is Liu Jinyi's favorite among all his grandchildren and is the most doted upon.
Due to this special status, Liu Jinyi would also tell her some work-related matters, like who are the allies and enemies of the Liu family, or which family's boy is the most suitable husband candidate...and so on.
So, Liu Xuelian is aware of the past grievances between the He Family and the Liu family, and knows that her grandfather suffered a great loss because of the He Family and has not yet recovered.
