Gadfrey is caught between a woman at the high end and a woman on the lowest rung of the community. 'She knew her husband would be smiling and smiled upon, hiding her existence in the darkest corner of his heart' What is Eliot showing us about community here?
Eliot is showing that in the 19th century, as nowadays, some people like Molly don't belong to society or even 'the lowest rung of the community'. The fact that Molly has a husband, Godfrey, who won't acknowlege her, prevents her from assuming her place in society. Her addiction to opium also prevents her.
Though it may seem that they are poles apart - at different ends of the social scale -Godfrey can't easily cut the ties between them. In the quote, above he seems happy in polite society but his scandalous relationship with the bar maid now drug addict, Molly, remains a part of him. Eliot is saying that divisions in society based on class are superficial; we belong to a common humanity.