What are Sheila's, and the rest of the Birlings', views on life?
I think that Sheila's view (along with Eric's view) changes as a result of the Inspector's visit and what they learn from that about the values of socialism.
It all starts off very self-satisfied and smug for the Birlings. They are delighted with themselves, with their expensive port (the Governor prides himself on being a judge of port, we find out), cigars, a dinner cooked by servants, and the satisfaction of knowing that Sheila and Gerald are engaged and to be married. Life looks brilliant, and Birling even launches into a monologue about the prospects for the future. His mantra, which he is iterating just as the Inspector comes in, is that "'a man has to mind his own business and look after himself and his own". Every man for himself.
After Sheila has found out what she has done to Eva Smith, and how her temper altered the course of Eva's life - and contributed to her suicide - she is immediately penitent and starts to rethink her attitude. 'But these girls aren't cheap labour', she tells the Inspector of her father's shop girls '- they're people'. She, and Eric with her, learns the central moral of the play: as the Inspector puts it, that 'We are members of one body. We are responsible for each other'.
Birling and Mrs Birling do not change at all throughout the play in terms of their attitude. Sheila and Eric do. 'The point is you don't seem to have learnt anything', Sheila tells her father. But she herself - by that point - has.