Marlow is a very curious character in the way that he has developed two sides to his character that come out depending on the class of woman he is with. In Act II, he discusses this with Hastings and explains the reasons for his strange behaviour, and why he is so shy and reticent with women of his own social class, and yet so gregarious with women of the working class:
My life has been chiefly spent in a college or an inn, in secclusion from that lovely part of the creation that chiefly teach men confidence. I don't know that I was ever familiarly acquainted with a single modest woman--except my mother--but among females of another class, you know--
The ellipsis of the ending of this quote hints heavily at Marlow's happiness to consort with working class women. Although this split personality of Marlow is used to create significant humour in the way that he is so voluble with Kate disguised and barely says a word to her when she appears as herself, his personality also conceals a somewhat more serious issue. The fact is that serving women were seen as "fair game" by upper class males. It is this class consciousness that has resulted in the differing personality of Marlow and that Kate is able to use to her advantage in "conquering" her husband.