After over six years playing Sinead, Katie will depart in heartbreaking scenes in the next few weeks.
In an interview in the latest issue of OK! magazine, Katie has opened up about her exit from the show.
"Selfishly, I was really pleased," the actress explained.
She continued to say how she had wanted to leave two years ago after bosses failed to give her a decent storyline.
That's when they told her about the cervical cancer plot they had planned for Sinead.
If I'm going to go, I want to go with a bang!
Katie added: "I said we should finish with the saddest ending because life's not a fairy-tale [and] I think a soap should reflect real life.
"I'm saddened that I'm leaving, but I want to create awareness.
"I'm so grateful for this storyline, it's like a nice big spring board to jump off rather than leaving in a taxi.
"If I'm going to go, I want to go with a bang!"
Sinead's cancer battle began a year ago as she ignored symptoms before eventually being diagnosed with the disease.
She postponed treatment as she was pregnant with baby Bertie at the time and she wanted to see the pregnancy through.
After the cancer progressed though, she gave birth to Bertie in January before beginning an aggressive course of treatment.
Things were looking up at a scan in July, which showed the disease was under control and not spreading.
But sadly, on her wedding day to Daniel, Sinead discovered a lump on her neck and tests days later confirmed her cancer had spread to her lymph nodes and liver and she only had weeks to live.
This week sees Sinead told the prognosis is now only weeks after life-prolonging chemotherapy has failed to make a difference.
Read more: Emmerdale airs huge confrontation tonight
Coronation Street announced last month that Sinead would die in heartbreaking scenes.
Katie then confirmed it was her decision to leave the show and she had not been axed, as some reports had suggested.
Read the full interview in this week's OK! out now.
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