Why did the Lady Dowager scold Lin Daiyu that "ghosts are not ghosts and thieves are not thieves"?

When drinking at a party, Jia ordered Jia Baoyu to propose a toast one by one. When she arrived at Lin Daiyu, Lin Daiyu handed the wine to Jia Baoyu's mouth, and Jia Baoyu drank it for her. So Jia Jia called Lin Daiyu "a ghost can't be a thief". I don't think she really called her names.

As the grandmother's favorite granddaughter, the grandmother can't scold Lin Daiyu just because of this trivial matter, maybe it's just funny. Besides, there is nothing indecent about it. As cousins who grew up together, this little thing is nothing. Even if everyone can see that they love each other very much, Jia also supports them together, so she won't scold Lin Daiyu for such a trivial matter, but may be poking fun at their feelings. If this incident is to punish Lin Daiyu, it is unlikely, because many things are usually more obvious than this incident and have not been taken into account.