After getting to the farm George and Lennie start talking to the Boss and he asks George what he's getting out of their relationship. This is Stienbeck again emphasising how one sided the relationship is.
While Slim and George are talking about Lennie, George confesses that Lennie is nuisance that he can't get rid of. This shows how the failure of the relationship is inevitable as George himself considers him more of a problem than a companion.
Lennie killing Curley's wife is