Katy O'Connor was the daughter of Sinead O'Connor and the late Rhys Ashworth. Sinead discovered that she was pregnant during a bus crash in November 2012, which killed Katy's father, Rhys. She decided that she didn't want the Katy, and after talking to Cindy Cunningham, decided to give Katy to her step-mother, Diane O'Connor, after her birth. However, Sinead realised that she didn't want Diane to raise her daughter.
In 2014, Sinead races Katy to hospital after she falls ill. However, Lindsey Roscoe believed that Sinead was lying for attention and didn't properly check Katy over. Sinead put blood in Katy's nappy after she accidentally cut her finger, but after confessing to Diane, Katy was taken away from Sinead and given to Diane to foster by social services. Sinead's brother, Finn O'Connor, allowed Sinead to quickly see Katy. After Sinead saw Katy, Diane returned to find Katy convulsing in her cot. Katy was rushed to hospital, but when Sinead arrived after being involved in a car accident caused by Fraser Black, she was informed by Freddie Roscoe that Katy had died.
The villagers became suspicious over Katy's death and accused Sinead of poisoning Katy. However, an autopsy revealed that Katy had cardiomyopathy, a heart condition which was undiagnosed. Sinead blamed a guilty Lindsey for Katy's death, going as far as to blackmail Sonny Valentine into getting revenge, lying to Lindsey that she is HIV positive after falling on a needle during a fight, and kidnapping Lindsey and Freddie before threatening to drive into a canal if Lindsey and Freddie didn't admit their affair.