Irony of the Conservative Image
The humble, religious, and conservative Charlotte Lovell is secretly the mother of an illegitimate child. Premarital sex in the mid-1800s, which is when this novel was set, was considered to be a shameful and forbidden thing especially for women.
Irony of Charlotte's Marriage
Charlotte is marrying the wealthy bachelor Joe Ralston chiefly to ensure that she -- and, more importantly, her secret daughter -- are materially provided for. However, as a condition of their marriage, Joe requires Charlotte to stop teaching and caring for the orphans and young disadvantaged children. To comply with her future husband's wishes will result in the end of her relationship with Tina.
Irony of Titles
Tina refers to Charlotte as "Aunt" and her cousin Delia as "Mother", having imitated the habits of Delia's children. In reality Charlotte is the mother and Delia is a second cousin. Unwittingly, Delia bestows the title of "Mother" on the wrong person.
Irony of Errand
Clement Spender is recruited by his relative Mrs. Manson Mingott to bring a wedding gift to the woman he secretly loves and wanted to marry himself.
Irony of Marital Choice
Clement Spender, despite his devotion to an unprofitable profession (he is an artist) and his inconvenient location (he lives in Italy), does in fact attract a wife who belongs to the same social class as Delia and Charlotte, but who is more proactive and willing to live at a lower standard of living. The woman he ends up with is not the one he initially loved or the one he impregnated, and he is less attached to her despite her efforts to catch him.
Irony of Sacrifice
Charlotte sabotages her impending marriage with Joe Ralston in order to ensure that her daughter is materially provided for. Delia persuades her to call the wedding off due to a return of her illness -- a claim that has a basis in fact but that is also exaggerated into a social fiction -- to avoid revealing the truth of Tina's parentage. As a way to smooth over the social fiction, Delia's husband Jim allows Delia to let Charlotte live in one of the unused family properties, with Tina. Charlotte gets the material stability she craves not through marriage but through her abandonment of it.
