Ramona Singer on Estranged Husband Mario: He's 'Dead' to Me
07/27/2015 AT 03:00 PM EDT
"I think once I became a 'celebrity' … and I was in the public eye – I think that bothered him," Singer tells PEOPLE Now while discussing her new book, Life on the Ramona Coaster, out July 28.
After The Real Housewives of New York City star learned of Mario's infidelity, she says it wasn't even that he "checked out of the marriage," it was like he became ''a different person.''
"There would be moments where he would be very warm and loving, and then other moments that he was really vicious and mean, and would bully me," says Singer, 58. "It was like, 'who are you?' It was scary, it was very scary."
"I don't recognize who he is today. That's the only way I can heal with it, because when he's across from me, he's not the man that he was two years ago. He completely changed."
Describing a moment she details in her book, Singer calls finding his mistress at their Southampton house "surreal."
"It just didn't seem like it was happening to me and him," she says. "He became another person. He's another person."
As for how she looks at him at him now, the RHONY star replies simply, "dead."
The Real Housewives of New York City airs Tuesdays at 9 p.m. ET on Bravo.