Published Wednesday, 18 September 2013
Sinitta speaks to This Morning on Wednesday. (© Ken McKay)
The surprising news was revealed last month when it was discovered that the X Factor boss was expecting his first child with New York socialite Laura Silverman.
It has been widely reported that Cowell fell for the 36-year-old after her marriage to New York property mogul Andrew Silverman broke down.
Speaking to This Morning's Phillip and Holly, Sinitta recounted the phone call Cowell made to her to inform her of the news.
"He called (to tell me) and I did think I was having a funny dream because he sort of sounded strange," she explained.
"I think he wanted to tell me but he hadn't chosen the words, so I kind of guessed, which is just like women's instinct, isn't it?"
Sinitta and Cowell have a long history together both professionally and personally and the mother-of-two admitted she was very shocked at what she had been told.
"Obviously we haven't been together for a while now," she said.
"But he has said to me a number of times over the years that he doesn't want children, so of course I knew I had to get on with my life because I knew I definitely wanted children.
"He has said he thought of (my children) as his own."
People think I am hanging on to this 'powerful superstar', but he is my friend, I have known him for 30 years so it's not weird.
Within hours of Cowell's impending fatherhood became public knowledge, Sinitta wrote on her Twitter page: "Something has just happened...half miracle, half nightmare #WakeMeUpIWantToGetOff."
The tweet caused a huge media stir, but Sinitta maintains she was just trying to understand what was going on.
"I didn't know the news was going to break so soon afterwards and I was just getting it into my head," she explained.
"I didn't want to phone him back and go on and on about it. There was no one else I could call, so I was just trying to see if there was anyone else in the world that I could just talk to about anything, because I didn't want to make the wrong call."
For years Sinitta has been seen to be part of a Simon Cowell 'harem' of ex girlfriends and Phillip asked her if the group dynamic was about to change.
"I can imagine (Simon) thinking "we are just a bigger family now"," she replied.
"He does seem very happy. They get along incredibly well together, she absolutely adores him.
"Obviously, as a close friend you are watching that, but he is the same when I am dating someone.
"I see him very happy, very relaxed. It's very different and surreal, but he does seem happy."
© UTV News