From the very beginning of the play She Stoops to Conquer the character of Miss Kate Hardcastle is indirectly portrayed as a woman who knows what she wants, and how to get it. Not only does she agree wit the idea of marrying Marlowe without knowing him, but she is secure in that she "will have him". This means that she is willing to do what it takes to secure the interest of the man who will eventually become her husband.
This being said, Kate is a remarkably strong female character and, as a result, her magnetic and dynamic traits complement perfectly Marlowe's lack of stability in terms of behavior. It is precisely Kate's willingness to transform and concede that makes the relationship between her and Marlowe concave and convex: their character traits fit perfectly together.
When Kate agrees to play the role of a maid, she does it knowingly; she has already tapped on Marlowe's weaknesses which, in their type of relationship, means that her own sense of security and strength will save anything that may endanger any chance of their getting together. This is evident in seeing how Kate reacts after seeing Marlowe's shyness manifest.
Ha! ha! ha! Was there ever such a sober, sentimental interview? I'm certain he scarce looked in my face the whole time.
Knowing that Marlowe has a weakness for common women does not represent a threat for an upper-class woman like Kate; if anything, this minor flaw in Marlowe's character is a challenge for Kate to conquer. Kate is quick to recognize both the good and the bad. She is so sure of herself that she sees no issue in fixing this problem as soon as possible. This is the benefit of having a strong female as a main character: it is the female who eventually ends up putting the pieces together and mastering the chain of events that will lead to the ultimate, happy ending.
He has good sense, but then so buried in his fears, that it fatigues one more than ignorance. If I could teach him a little confidence, it would be doing somebody that I know of a piece of service.