The best part of the text to look at in order to answer this question would be the description of Mary and what she thinks of her husband as he returns from work. Part of the excellent use of irony in this passage relates to the way in which Mary is presented as a wife whose existence is built around her husband's happiness and would do anything for him to make sure that he is happy and well. Consider how she greets him with a smile and gets him a drink so he can put his feet up. Note how the following quote describes her feelings towards him:
She loved to luxuriate in the presence of this man, and to feel--almost as a sunbather feels the sun--that warm male glow that came out of him to her when they were alone together.
The somewhat hyperbolic comparison of Mary Maloney standing in front of her husband and soaking up his rays as if she were a sunbather points towards her total and almost pathetic devotion towards him.
However, having said this, it seems obvious that her husband is indifferent towards her affections and feelings. Although she is pregnant, he lets himself be waited upon, and then destroys her world in an instant by probably telling him of how he plans to leave her for another woman. Whilst there is tremendous devotion in this marriage, it is therefore all one-sided, as Mary is married to a selfish man who does not love her in the same way that he is loved by her.