I can't help thinking about this girl— destroying herself so horribly —and I've been so happy tonight.
Sheila shows sympathy towards Eva but it doesn't necessarily show she is any better than her father. Referring to her as 'this girl' shows a condescending tone. This quote is also very focused on how Sheila feels as a result showing that she's not really thinking about Eva but herself
We've no proof it was the same photograph and therefore no proof it was the same girl
In Act 3 Priestley creates some doubt among the audience over whether Eva really existed. This builds tension up to the moment when the Birlings receive the telephone call and also puts the audience in a situation in which they are also denying her existence like the Birlings.
'Lively good-looking girl' and 'pretty'
Eva is continually described based on her looks, highlighting the gender stereotyping at the time and allowing Priestley to highlight how this was how many women were classified and valued at this time.
Girls of that class
In Act 2 Mrs Birling makes it clear that her problem with Eva lay in the social class she belonged to. 'That' suggests something which is distant, separate, much like the working class were from the upper and middle classes.
a young woman died in the infirmary
At the start of the play in Act 1, the words here evoke sympathy from the audience due to the connotations of innocence. The Inspector's direct tone here is shocking for the audience which creates further sympathy at the start of the play.
a good worker
This shows how important work was to people of Eva's class, they worked for survival not luxuries like Birling with his factory. This is a direct contrast with Sheila and Mrs B who do not work and highlights the inequalities of the time.
You've had children. You must have known what she was feeling. And you slammed the door in her face
The Inspector's accusations here convey that Mrs Birling has committed a grave sin. The Inspector uses highly gendered language here to show how Mrs Birling's part was worse as she ignored a mother's instinct to help another mother.
Miss Birling has just been made to understand what she did to this girl. She feels responsible.
This reveals a lots about the Inspector's motives - he is here to cause them pain and to feel guilt for their part in Eva's death. He goes on to suggest that if Sheila leaves the room she'll only feel responsible herself when he actually wants her to understand the immorality of her supposed 'respectable' family.