The narrator's friend Jeff is unfair in his business dealings. He is running a scheme where he gets men to pay $2.00 to be considered by a widow (with $2000) as a husband. He not only plans to turn away every man, while keeping the $2.00.
However, Jeff wanted to at least have a "lady" who exists to give the process some legitimacy. His friends Andy, also unfair as he is a partner in this scheme, doesn't even feel that they need that:
Why should there be a lady? When they sell a lot of watered
stock on Wall Street would you expect to find a mermaid in it? What has a matrimonial ad got to do with a lady?
Andy goes even further than that, double-crossing his own business partner. He secretly goes to see Mrs. Trotter - the woman they get to be the "ruse" - by the name of William for 3 months, getting her to fall in love with him. He convinces her that he must have the $2000. She convinces Jeff to give her that money, which she then gives to him. So, he protected the con by making sure that the woman didn't fall in love with someone else who would demand the $2000.
Ironically, Jeff blames Mrs. Trotter for letting emotion control her emotions, but it is his own sympathy for her that causes him to give in:
"'It's a sad thing, Andy,' says I, 'to think that we've been the cause of the breaking of a woman's heart.'