The former glamour model claimed her ex-husband still hasn't told her why he wanted to get divorced - their split was finalised in 2009 - and insisted their relationship has become too fractured to even be friends.
Speaking to The Sun on Sunday newspaper's Fabulous magazine, she said: ''I never wanted a divorce from Peter. That was his decision, not mine.
''He's never, to this day, told me the reason why. We don't speak. Too much has gone on. I'll never speak to him again.''
Katie - who divorced second husband Alex Reid in 2011 and has been married to Kieran Hayler since 2013 - admitted she ''was devastated'' when their relationship came to an end, and explained she doesn't cope well with being single.
She added: ''I can be bad ... When Pete left me, I was devastated and I went out drinking and partying.
''It was my way of melting down - I felt like everyone hated me and none of it was my decision. My life fell apart.
''When I'm single, I'm bad. When I'm in a miserable relationship, I'm bad, but when I'm in a good relationship, I'm 'happy Kate.' ''
The novel's author saw a cut of the film and loved each of the changes the movie's director had made.