Since "The Jilting of Granny Weatherall" involves stream-of-consciousness there is a great deal that goes on in Granny's mind that does not find itself in reality; as a result, the outcome is very different from what is expected.
1. Perhaps the greatest example of the outcome turning out to be very different from what is expected is at the end of the story when Granny thinks the priest is merely tickling her toes as he anoints her for the Sacrament of Extreme Unction and Granny dies, but thinks she merely has taken a deep breath and blown out the blue light. Instead, she is taken surprise by death.
2. Another major example of irony of situation occurs as Granny feels in two incidences that the pillow "rose and floated under her" and "about her shoulders and pressed against her heart and the memory was being squeezed out of it" when her consciousness is active only; no pillow is moving. Instead, she is probably having heart problems.
Both instances end is what is called a "violation of expectation"; certainly, there is an irony of situation.