Mrs Birling: The Ultimate Upper-Class Hypocrite
Mrs Birling is your classic wealthy snob who thinks she's better than everyone else. Her name Sybil means "prophetess," which is pretty ironic since she's actually clueless about what's happening around her - she's the last person to figure out Eric's drinking problem and completely misses the point of the Inspector's message.
Priestley uses her as a symbol of upper-class hypocrisy. She looks down on "girls of that class" whilst being completely oblivious to how her own actions hurt people like Eva Smith. She's got zero self-awareness and genuinely believes she's a good person, even though she shows no empathy when Eva dies.
The really telling thing about Mrs Birling is how she maintains her coldness throughout the play. She's described as "a rather cold woman" and proves it by dismissing the whole situation as "absurd business" that everyone should just forget about. This shows how disconnected the wealthy are from real consequences.
Her marriage to Mr Birling was basically a business deal - she brought social status, he brought money. This perfectly demonstrates Priestley's criticism of capitalism, where even personal relationships become transactions rather than genuine connections.
Key Point: Mrs Birling's character shows how privilege can make people completely blind to their own faults and the suffering of others.