Katie, who is pregnant with Kieran's second child, posted three notes on the social networking site this morning (23 May) with the captions "my thought", "this has been the case" and "sooo true".
Yesterday, Kieran took to Twitter and wished Katie a happy birthday, while also vowing to repair her heart. It was the first time he has publicly spoken since it emerged he had cheated on Katie with her best friend Jane Pountney.
Former glamour model Katie then logged on to thanks fans for their birthday wishes, however she chose to ignore Kieran's tweet.
This morning, Katie logged back in and alongside a tweet that said "my thought" she posted the slogan: "Defeat your enemies with success."
She then posted the message, "the saddest thing about betrayal is that it never comes from your enemies," alongside a tweet that read: "This has been the case."
Finally, Katie tweeted: "Sooo true." Alongside it, she uploaded the picture message: "Trust takes years to build, seconds to break and forever to repair."
Katie turned 36 yesterday and it was the first time she had used Twitter since discovering that Kieran had cheated on her. On 7 May, Katie shocked fans by announcing that she is to divorce Kieran for having a "sexual" relationship with her good friend Jane for seven months.
The soon-to-be mum-of-five then went on to brand Kieran a "disgusting human being", adding that Jane was a "home-wrecker" and a "s*ut".
Two days after the surprising news broke, Jane spoke out for the first time and admitted that she had been having an affair with Kieran. She said that she "deeply regrets" what happened.
Kieran had, until yesterday, remained silent, although it was recently reported that Katie had asked him to move out of their shared West Sussex house and into a cabin in the garden while she thinks about what she wants to do next.
In January 2013, Jane had been among the very few guests at Katie and Kieran's wedding in the Bahamas.
Making it worse for Katie has been the fact that news of the affair came just three days after she publicly announced she is pregnant with Kieran's second child.
The couple are already parents to son Jett, who born last summer.
Since her tweets announcing Kieran's affair, Katie has remained largely absent from the spotlight. Her rep has said she is focusing on her unborn baby and that she thanks fans for all their messages of support.
Last week, it was claimed that Katie had cancelled plans to celebrate her 36th birthday with a lavish pink and white-themed bash organised by Kieran and Jane.