The irony of the situation is that she lives with them but never realizes the truth until the end.

irony 是名词，意思是"讽刺"，指一种情况或事件的实际结果与预期或表面现象完全相反，从而产生荒谬或幽默的效果。这个词来自希腊语 eironeia（假装无知），后来演变为表示"反讽"的含义。