Eva Smith represents the proletariat, who has been exploited by the bourgeoisie - the Birlings, as part of the capitalist ruling class abuse this for their own profit/benefits.
...The Inspector hints at social revolution when he speaks of "fire and blood and anguish" if the bourgeoisie do not change their self-serving behaviour.
While three of the five characters do not change their hearts or minds, the audience takes some comfort in the fact that Eric and Sheila do for, as members of the younger generation, they represent hope for the future of British society