Writing in her autobiography Reborn, in an extract which is being serialised in The Sun, the mum-of-five talks candidly about the tumultuous time in her marriage when she discovered husband Kieran had been unfaithful to her while she was pregnant with her daughter.
Although going on to admit that she doesn't believe a child should ever be brought into the world to save a relationship, she explains how Bunny's arrival healed the damage between her and Kieran.
'If there's one thing that kick-started the turnaround in the relationship between Kieran and me it was my little Bunny's arrival into the world,' the 38-year-old star writes.
'In lots of ways she became the fresh start we both needed.
'Normally, I wouldn't recommend having a baby to save a relationship - more often than not the strain breaks an unstable marriage. But I guess because we had kids already it wasn't such a shock to the system.
'If she'd been my first and Kieran had behaved as he did, I wouldn't have coped. It's funny how good things happen when you least expect them.'
Katie goes on to explain how impressed she was with her husband's commitment when she gave birth to their daughter a month early, staying at the hospital while also seeking treatment for sex addiction.
'Kieran did make those first few weeks of looking after Bunny much easier,' she says. 'He was being determinedly hands-on.
'He'd said that as a result of his ongoing treatment he'd refocused his life and was discovering who he truly was - the family man I knew he had in him all along
'After a while, my long succession of bad days gave way to some good ones,' Katie explains.
'It was as if Bunny had breathed life into our relationship, and I will always see her as my little ray of sunshine.'
Bunny, now two, is one of Katie's two children she shares with Kieran, and one of her brood of five in total, including Jett Riviera Hayler, Princess Tiaamii Crystal Esther Andre, Junior Savva Andreas Andre and Harvey Price.