Mrs Birling claims that “a girl of that sort would [not] ever refuse money”, as she assumes that due to her lower class origin, Eva is inherently greedy. Despite this, Eva is presented as a moral force, who never takes stolen money and won't marry Eric just for his wealth and social status.
➔ This is in contrast to Eric, who steals money (from his own father), despite coming from the upper classes. This makes Mrs Birling’s assumption of Eva’s greediness ironic.