There are a number of ironical moments in the story.
It is ironic that Delia washes someone else's clothes and makes money on it, but her own clothes remain dirty.It is also ironic that Delia is a very strong person but she can not stand up to her abusive husband due to the societal rules at that time, she knew that she would be killed if she stands up to him or leaves him because of very these societal rules. It is ironic that Delia makes money but her mistress Bertha makes use of the money.
The irony in the story helps to emphasize that not all decisions and conflicts are obvious and also that morality is not always straightforward.
Is it wrong or right that she leaves her abusive husband to die, when he is bitten by a snake? Is it wrong that she works on Sundays?