What do you think is discussed between Doran and Mrs.Mooney in their private conversation? Why didn't Joyce include the specific conversation?

Doran has had an affair with Mrs. Mooney’s daughter, Polly. The text seems to imply in various ways that Mrs. Mooney actually encouraged the affair when it happened by turning a blind eye to it. Initially, when Mrs. Mooney starts the boarding house, she sends Polly off to a corn-factor’s office where she is to work as a typist. However, she recalls her to the house to protect her from a certain Sherriff’s man of bad repute who develops an interest in her. Afterwards, she wants to send Polly back to the office as she notices that her marriage prospects with the young men of the boarding house are quite low. Mrs. Mooney is interested in seeing Polly married off to a nice young man. This is why she pretends not to see the developing relationship between Polly and Doran until she judges that the two have reached a point of no return. She hopes that at this juncture, Doran would be obliged to take her daughter’s hand in marriage.
It is to be thought then that Mrs. Mooney talks to Doran about the romantic relationship between him and her daughter, and how he could “make up for the loss of Polly’s honor.” Mrs. Mooney wants the two to marry. Doran, on the other hand, has conflicting ideas about what he needs to do.
Joyce omits the specific conversation between Mrs. Mooney and Doran because its nature and outcome is kind of obvious. Conventionally, Doran is expected to marry Polly regardless of whether he loves her or not, especially because of the public and sexual nature of their relationship.