updated 10/10/2011 AT 8:00 AM ET
•originally published 10/10/2011 AT 8:20 AM ET
“I thought she was a 28-year-old heterosexual girl, because that’s what she looked like to me. And she’s a 40-year-old gay woman,” O’Donnell, 49, tells ABC’s Nightline in an interview airing Monday night.
She adds with a laugh: “My gaydar was way off!”
But O’Donnell, who recently said she’s in love, thinks maybe it’s a good thing she thought Rounds was straight. “I think if I had known that she was gay, I wouldn’t have been brave enough to talk to her,” she says.
O’Donnell’s new nightly talk show, The Rosie Show, debuts Monday on the OWN network.