The 50-year-old star, who retreated from the spotlight after an appearance at the 2014 Elle Women in Hollywood Awards prompted speculation that she had had plastic surgery, recalled the "pretty painful" moment she overheard strangers negatively discussing her looks.During an appearance on US radio station SiriusXM's "Jess Cagle Show," Zellweger said she was sitting next to two women and a man "on a subway in London" when they started discussing celebrities. "They were talking about... how Hollywood ladies are so silly, and especially that Ren\u00e9e Zellweger," she said.Zellweger said they went on to say: "How could she do that? Why would she go and have surgery on her face like we wouldn't know? She doesn't look like herself, and you can't just do that where you go and don't look like yourself, cause we expect you to look like yourself."She said the encounter left her momentarily stunned: "I thought, 'Wow, that's interesting. Anyway, here's my stop.'"The famously private star, who plays Judy Garland in a forthcoming biopic, said things got even more awkward when the man got up just before her stop, looked up and recognized her."He said, 'Oh God, you're not, you are! But you look just like yourself!' And I said, 'Yeah, it's funny how that works, isn't it?'"While she was hurt by the public bashing, Zellweger insisted that the interaction only served as a reminder that she needed to maintain a positive outlook on life."It's only momentarily where you go, 'Jeez, wow, that's pretty painful.' But I don't live in that," she said. "It just visits my life here and there and I'm not really privy on that stuff until someone sends it to me. I don't seek it out."And I'm busy! You know, I have dogs and they have to have shots and they need pills twice a day. There's a lot, you know. I have other things to do."Zellweger has previously denied undergoing surgery, saying in a statement that she was "living a different, happy, more fulfilling life."CNN has reached out to Zellweger's representatives for comment.