Character Analysis
Freud doesn't reveal the true identity of the "Irma" who appears in his Dream of Irma's Injection. Instead, he says that she was "a young lady who was on very friendly terms with me and my family (2.1.15), that she was suffering from "hysterical anxiety" (2.1.15), and that she was a widow (2.1.39).
Freud also reveals that he found Irma difficult to work with—particularly because she refused to accept his beliefs about the true nature of her anxiety. This dissatisfaction, which tapped into Freud's deeper concerns about the validity of his methods, was one of the root causes of the dream in which Irma appears.
As Freud's analysis notes, however, the Irma who appears in the Dream of Irma's Injection doesn't just represent the real-life woman Freud was treating. Dream-Irma also shares a number of characteristics with another young woman of Freud's acquaintance—someone who was not one of his patients but whom he would have liked to treat. Irma also shares some characteristics with Freud's wife, Martha.
As Freud explains, the Irma who appears in the dream is the product of dream-condensation and unification. She represents a number of women in Freud's life, and her presence in the dream reveals hidden aspects of Freud's relationships with all of them.