Template:InfoboxKathy is introduced shortly after her daughter Sarah Barnes. Kathy is strictly training Sarah for numerous swimming contests and a future career in the sport. Sarah feels suffocated by Kathy's pressure and finds support in the form of boyfriend Rhys Ashworth. Kathy's husband Mike and their second daughter Amy then arrive. Kathy sees Sarah's boyfriend Rhys Ashworth as a threat to her hope of Sarah becoming a swimmer. Kathy then sleeps with Rhys and blackmails him into breaking up with her. During a massive row over Sarah and Rhys getting back together at Mike and Kathy's anniversary party, Gilly Roach inadvertently shouts out that Rhys and Kathy slept together, in front of Sarah, Amy and Mike. Sarah is hurt and disgusted with Rhys and Kathy, while Amy is left shocked and distressed by the revelation. Mike is furious. Backed up by Amy and Sarah, he orders Kathy to leave, which she does. Kathy returns and gets back together with Mike after the two decide to reconcile for the sake of their daughters. Amy gives birth to Leah Barnes and Kathy feels ashamed. To cover it up, Kathy decides to raise Leah as her own. Kathy leaves to stay with her mother for a short while. In this time, Amy bonds with Leah and declares she wants to raise Leah, she also tells everyone she is Leah's real mother. Kathy realises she will lose Leah and kidnaps her. Eventually Leah is returned to Amy as Kathy moves to her mother's to recover from trauma.
Kathy returns in October 2007, and finds Ste Hay living with Amy. Kathy and Mike are not happy and throw Ste out. Amy then leaves with Leah and moves in with Ste. Kathy phones the social services which excludes her from her daughter even more. Kathy discovers Sarah and Rhys are back together. Their relationship leads to the start of Kathy's vendetta against the Ashworth family. The family begins getting strange phone calls, vandalism on their house and even a Tupperware box full of faeces. The Ashworths begin to accuse several people including Ste and even own family members Hannah and Beth. Whilst throwing a brick through the window of the Ashworth family business, Drive 'n' Buy, Kathy loses a nail. She goes to Evissa for a manicure and tells Carmel that she took the nail off after it became loose. Carmel turns detective and finds a broken nail outside Drive 'n' Buy. She then reveals Kathy as the vandal. Kathy, Mike, Sarah, Amy and Ste are confronted bySuzanne, Nev, Rhys, Josh, Hannah and Beth. Kathy also gets jealous of Zoe Carpenter and falsely accuses her and Mike of cheating. Although he had always previously supported Kathy throughout all of her various issues while at Hollyoaks, this accusation, coupled with Kathy's vendetta against the Ashworths, finally proves to be the last straw for Mike. Unable to cope with Kathy's behaviour any longer Mike tells her to leave. When she refuses, Mike throws her out, and Kathy goes to stay with her mother. In January 2008 Mike subsequently files for a divorce.
In October 2009, Sarah dies during a parachute jump. Mike phones Kathy to tell her the bad news. However, she does not attend Sarah's funeral.