Frank's Name (Situational Irony)
Frank himself realizes the irony of his last name: "The crazy part is our last name. Money. Of which we had none" (40). The word "money" is short, unambiguous, and impactful, and it's no wonder that the people Frank meets cannot help but assume with a name like that he's got to have money. Unfortunately for them—and him—it's not the case, and the irony is hard to ignore.
Stealing (Dramatic Irony)
When Frank bursts into the house and the doctor sees him, the doctor yells out in fright, "There's nothing to steal here!" (110). This is ironic because: 1) the doctor stole many things from Cee—her fertility, her peace of mind, her health, her power; 2) there is something to steal here, but it's a person, not a useless trinket.
The Doctor (Situational Irony)
There is a broad consensus that doctors are supposed to (and mostly do) help, cure, and, as the Hippocratic Oath states, do no harm. Yet the tragic irony in this novel is that Dr. Scott does an immense amount of harm to Cee, thus belying her initial impression of him as kind, generous, and full of succor for women.
Home (Situational Irony)
Given all the antipathy both Cee and Frank show towards Lotus, there is a degree of irony in the fact that this ends up becoming their home at the end. Only Lotus is able to heal them physically and mentally; only Lotus can give them relief from their demons. It is life outside Lotus that does so much harm to the siblings, and once they are back within its folds they can see it for what it really is.