Dolly Parton is one of the most important singer-songwriters in the country genre, as well as one of the best-selling female artists of all time. That success has come at the price of having her personal life subjected to all manner of tabloid scrutiny, and in an interview to promote her new memoir 'Dream More,' the legendary songbird opened up about her career, plastic surgery procedures, and love life -- including the often-repeated rumor that she is secretly gay.

It's a story that has followed the singer for decades, based on speculation about the true nature of her relationship with her longtime assistant Judy Ogle, with whom she has been friends since childhood. Parton told 'Nightline' correspondent JuJu Chang that people "just think that you just can't be that close to somebody. Judy and I have been best friends since we were like in the third and fourth grade." She categorically denied that their relationship is anything more, adding, "We still just have a great friendship and relationship and I love her as much as I love anybody in the whole world, but we're not romantically involved."

Those aren't the only rumors that have plagued Parton's 46-year marriage to her husband, Carl Dean. "I've been accused of being involved with every man I'm ever seen with or worked with," she observed. "Maybe I have, maybe I ain't. I never tell if I have. But you know people [are] always saying that."

Parton has never been shy about admitting that she has had cosmetic procedures, as it's something she's completely confident about. "I really think if there's something you need to do, want to do, can afford to do and got the nerve to do, I think you should do it if it's gonna make you feel better about yourself," she related. Asked about aging with breast implants, the irrepressible singer quipped, "I don't think they age! My girls are doing pretty good."

Not good enough, apparently, for the judges of a Dolly Parton drag queen lookalike contest. Parton said she entered one on a lark, with nobody present knowing they were competing against the real Dolly. "All these beautiful drag queens had worked for weeks and months getting their clothes," she shared with a laugh. "So I just got in the line and I just walked across, and they just thought I was some little short gay guy -- but I got the least applause."

Parton's new book, 'Dream More,' is available Tuesday (Nov. 27).

Watch Dolly Parton's 'Nightline' Interview