It's polite to tell someone before you leave.
Marge is at a party and finds out that her kids at home need help.
Marge wants to go home quickly.
Marge hastily tells the host that she needs to leave for an emergency.
Marge leaves the party without informing anyone.
The host says that it's fine and understands Marge's dilemma.
The host tries to find Marge but can't, so she thinks that Marge doesn't like her.