The 36-year-old was left stunned and heartbroken when she learned Kieran had been enjoying a sexual relationship with her best friend Jane Pountney – while Katie was pregnant with Kieran's second child.
Katie's made no secret of her hurt and anger, tweeting various messages – and one picture – slamming both Kieran and Jane for their actions.
But, over the weekend, the pregnant model appeared to be embracing a more positive attitude looking forward to the future.
Katie tweeted a series of inspirational and motivational messages, including: "There are so many beautiful reasons to be happy."
The star also shared the message, "Loyal people still exist", and another reading: "You never know how strong you are until being strong is the only choice you have."
Perhaps alluding to her past comments about Kieran and Jane, she also tweeted the note: "You own everything that happened to you. Tell your stories. If people wanted you to write warmly about them, they should've behaved better."
Another message read: "Life is short, there is no time to leave important words unsaid."
Katie has been keeping a relatively low profile since news of Kieran's betrayal became public knowledge on 7 May.
Her first public appearance came on 4 June, when she stepped out looking like a human rainbow at a photocall for her latest venture.
While there, she did speak briefly about Kieran to assembled reporters, suggesting the truth of what happened was yet to be fully revealed.
You've only heard bits, but if you heard the whole truth you'd be like, 'Jesus'," she said. "Trust me, if everybody knew what was going on they'd be like, 'How the hell is she sitting here today?', because it's that bad."
Kieran, meanwhile, has made no secret of his desire to win Katie back, tweeting her a birthday message last month and insisting in newspaper interviews that Jane meant nothing to him.
Katie and Kieran married in the Bahamas in January 2013 after a whirlwind romance. Their first son together, Jett, was born that summer. Their second child is due later this year.
Katie is also mum to sons Harvey and Junior, and daughter Princess, from previous relationships.
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