Mimi was the girlfriend of former gangster Lips Manlis. She was attractive woman with short dark hair. In addition to being Lips' girlfriend, she was a member of the criminal gang in her own right.
After Lips reformed and changed his name to "Bob Honor", he refused to associate with Mimi or his old gang anymore. Angry, Mimi arranged for the warehouse Bob was guarding to be burnt down so he would be fired. However, Bob found the firebomb before it detonated and was praised as a hero.
Mimi and the gang then kidnapped Bob, but while Mimi was out on an errand, Lips broke free and began to force the rest of the gang to police headquarters to surrender themselves. Mimi got back in time to see what was happening, and swerved her car in front of Bob's truck. The crash crippled her hand, but she was able to escape. Bob decided not to pursue her and freed the captured gang from the burning truck. He held them until Dick Tracy arrived.
Mimi's hand needed to be amputated, which caused her great distress. She went to the boat owned by her dope-peddler associate Toyee to hide-out. Toyee captured Dick Tracy and Pat Patton when they came to his boat in search of Mimi. Toyee tried to drown the detectives, but they were rescued by Chief Brandon and Junior. Toyee and Mimi fled to Toyee's waterfront hideout, but Tracy quickly caught up to them. He captured Mimi and her gang, but while Tracy was arresting Toyee, Mimi stabbed Pat and escaped.
Mimi returned to her residence in the city. She had her gang kidnap Bob and drug him. While he was drugged, Mimi married him and then attempted to make Bob revert back to his criminal ways. Tracy enlisted Kitty Manlis (Bob's ex-wife) to find Bob and help him. When they arrived, Bob dropped Kitty and Tracy into a pit, making Tracy believe that Bob was a criminal once again. However, Bob soon revealed that he had done it to ensure Tracy's safety while he captured Mimi's gang. Realizing that she had been defeated, Mimi committed suicide by drinking a vial of poison.