She was Joe Driscoll's elderly neighbor who lived across the street.
Irma first met Dexter Morgan when he came to Dade City after he inherited Joe Driscoll's house. Dexter begins to suspect that Joe had been murdered, and Irma mentions that a "cable repair man" had visited Joe the week before.
At the end of the episode, it is revealed (to the audience) that the "cable repair man" was Brian Moser. She is seen opening her door to be greeted by Brian, who is dressed as a cable repair man. Brian then enters her house and closes the door behind him. He then presumably kills her. It is not known whether he made it look like a heart attack as he did with Joe Driscoll, or if he killed her in another way and disposed of her body.