Blackmailed Ned Ashton into marrying her
Faked a pregnancy to trap Nikolas into marriage 
Katherine arrived in Port Charles in 1993, using the name Katherine Crawford. She claimed that she was a long-lost friend of Dominique Baldwin, and hit up Dominique's widow, Scott Baldwin, for $250 thousand. Then Scotty's longtime friend, Lucy Coe, learned Katherine's true identity, Katherine Bell, the daughter of the cook at Dom's childhood home. Scott made excuses for Katherine, and went as far as to name her head of public relations for Deception, Lucy's company. Scotty and Katherine were falling hard for each other. One problem, Katherine had a lover, Damian Smith, and the two had planned to take Scotty for all that he was worth. So Damian teamed up with Lucy to stop Scotty and Katherine from marrying. They revealed that Katherine had been conning Scotty from day one. Scotty left Katherine at the altar and never looked back. Katherine later discovered that she was actually the sister of Dominique, the illegitimate daughter of Dominique's father and the cook.
Next Katherine went after the wealthy Ned Ashton, whom she managed to blackmail into marrying her. This marriage was short lived when Ned's other wife, Lois Cerullo, popped out of the cake at Katherine's birthday party. Ned had married Lois, his true love first, thus making his and Katherine's marriage void. Katherine thought that she had the leverage to stay a Quartermaine when the Quartermaine butler, Reginald, poisoned her. But A.J. made it appear that she had poisoned herself. Katherine did come out of the marriage as owner of Deception Cosmetics.
In 1994 Katherine co-founded the Nurses Ball with Lucy Coe, with the two usually brawling or trying to outdo each other onstage. At the 1997 NB, Katherine took her first steps after being shot. In 1998, Lucy mourned for her presumed-dead rival. Katherine participated for the last time in 1999, only months before her murder.
In 1995 Katherine became involved with good guy, Mac Scorpio. Mac was the first man who could see through Katherine's games. After Katherine was shot accidentally by Stefan Cassadine in 1997, she and Mac called it quits. Katherine had fallen for Stefan, who never left her side, but he was married to Bobbie Jones when Stefan and Bobbie divorced, he pursued a romantic relationship with Katherine. Eventually Stefan and Katherine became engaged, they celebrated their engagement with a ball at Wyndemere, but the happy night ended in tragedy. Katherine realized that Stefan was still in love with Laura Spencer, and the he was Nikolas' father. Katherine fell into a trap created for Helena, and fell from the parapet.
Everyone thought that Katherine was dead, Stefan was even put on trial for her murder, but it was discovered that she survived, due to experimental drugs, provided by Helena Cassadine. She returned to Port Charles, and moved back into the Quartermaine mansion, by invitation of Edward Quartermaine. But it was not long before she left. She also began having an affair with Nikolas Cassadine, after Helena told her that Nikolas would be a good way to get back at Stefan. But Katherine came to care about her boy toy, and she was rather jealous when she saw him with his friend Emily Quartermaine.
Katherine arranged for Liz to see her and Nikolas in a compromising position. When Nik realized, he angrily broke it off with Katherine. She faked a pregnancy to win him. After repeated attempts at impregnating herself failed, the doctor told a devastated Katherine that the drug Helena injected her with to keep her alive had somehow destroyed her ability to have children.
Katherine initially refused Nik's marriage proposal, playing her scheme brilliantly. As the wedding day (at Wyndemere, by Nik's request) approached, Katherine planned to pick a fight with Laura at the reception, causing a "miscarriage"; after learning they could have no more children, Nikolas would stay with her out of guilt.
Unfortunately for Katherine, she confided these plans in a comatose Helena. Helena would not allow her grandson to be manipulated into a sham marriage. Helena had regained her movement weeks earlier, and, disguised as Laura, pushed Katherine off the same parapet shortly before the ceremony. There was no miracle drug to save Katherine the second time around. Her killer was never brought to justice.