Michelle Rounds (left) and Rosie O'Donnell
10/10/2011 AT 08:20 AM EDT
was attracted to Michelle Rounds the moment she saw her
in a Starbucks this summer. But she never thought it would be reciprocated.
"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.