Dolores first appears serving a few barflies at the Pacific Electric Red Car Trolley Terminal Bar, with Eddie Valiant being one of them. She notices when Eddie loses his composure after one of the barflies makes fun of him, believing he works for toons. She is quick to garner the barflies' sympathy for Eddie once she reveals the truth behind Eddie's hatred of toons to them, explaining that his brother Teddy Valiant was killed by a toon by having a piano dropped on his head. She apparently cares for Eddie, and even helps him when the latter explains about Judge Doom and the Toon Patrol, who are all after Roger Rabbit because he supposedly murdered Marvin Acme. She also seems to know about his will, as she warns Eddie of how Cloverleaf Industries had placed the highest bid for Toontown and will acquire it at midnight if Acme's will fails to show up by then.
She plays a larger part in the film's climax, where she saves Eddie from almost being killed by Judge Doom and the Toon Patrol when they come for Roger at the bar by providing a drink that causes Roger to erupt like a high-pitched steam whistle so Eddie could fight off the Toon Patrol and rescue Roger. She armed herself with a bat in case things escalated further. For her part in Eddie and Roger's escape, she was presumably fired as a result, which was fine for her because she admits, "Stuffing olives for a living wasn't for me anyway." Following the climatic battle at the Acme Factory that saw the death of Judge Doom, Dolores arrives with Benny the Cab, Lt. Santino, and the LAPD, where Eddie proves Roger was innocent of murdering Acme while Doom was guilty of murdering Acme, R.K. Maroon, and Teddy Valiant, along with the attempted murder of everyone in Toontown.
She is last seen walking beside Eddie as they, along with Roger and Jessica, enter Toontown together while accompanied by all the other toons in the film singing "Smile Darn Ya Smile".