NEW YORK —  Rosie O'Donnell says her talk show lost its appeal after she got into an on-air dust-up with Tom Selleck -- and says she's "not that nice."

O'Donnell made headlines when, in May 1999, she lambasted Selleck for appearing on NRA ads when he visited The Rosie O'Donnell Show to promote his new movie, The Love Letter. 

"The first few years I could hardly believe what was happening . . . these big stars like Julie Andrews and Barbra Streisand sitting next to me," O'Donnell tells Isaac Mizrahi in an upcoming interview on Oxygen's Isaac Mizrahi Show. 

"Then it got a little crazy with the whole Tom Selleck NRA thing . . . 

"I do like [not having a show], but it's hard to say that without people not thinking that you're ungrateful," she says. 

"I'm so grateful. It's given me and my family everything I could ever dream of . . . But that's only part of who I am and after a while it . . . became a little oppressive. 

"Everyone thought, 'Oh, you're so nice.' I'm not that nice. I'm a very biting, caustic, sarcastic person." 

O'Donnell spends the majority of her interview with Mizrahi getting the short haircut (courtesy of stylist Ashley Javier) that she's worn since leaving her show last spring. 

O'Donnell also explains to Mizrahi why she decided to bolt "Rosie." 

"The temptation was to stay at the job even when the thrill of doing it was gone," she says. "That was just money, and you know what Isaac, I've got enough money." 

She also talks about her long history of depression. 

"For years I fought going on medication . . . but after Columbine I had no choice because I couldn't sleep well," she says. "[Columbine] affected me in a way that was hard to articulate." 

O'Donnell, who came out as a lesbian shortly before her show went off the air, also addresses critics who scolded her for "hiding" her sexuality. 

"I think you can live your life as a gay person in the way that I did -- never hiding it from anyone, attending every event with [galpal] Kelli [Carpenter], never pretending to have a boyfriend. 

"These people were going, 'She was pretending' [to be straight]. 

"I don't feel like I ever pretended anything. You've got to do what's true for you." 

O'Donnell's interview airs Monday, Oct. 21 at 10:30 p.m. on Oxygen.

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