Pippa Middleton has claimed she was “publicly bullied” in the wave of publicity after she was a bridesmaid at her sister’s wedding.
Ms Middleton said she found it “difficult” to cope following the 2011 event and singled out internet commenters for telling lies about her.
She said it was unfair how people could write something on Twitter or Facebook anonymously and said she got through it by limiting what she read.
She said: “I think people can say something about you online or on a web page when they would never say it to your face – but they think that’s OK.”
Ms Middleton, 30, was speaking in her first TV interview, which she gave to US TV network NBC.
She said that after taking part in the wedding of the Duchess of Cambridge, her older sister, and Prince William, she had found the attention that came her way to be “completely unexpected”.
Ms Middleton was named “Rear of the Year” in one poll and a Facebook page devoted to her derrière got 200,000 “likes”.
A public debate ensued as to whether she had undergone buttock surgery because her behind was deemed so shapely. Over the subsequent three years, however, things changed; her fans stopped swooning and instead critics have written numerous articles asking if she is cashing in on her sister’s fame.
Ms Middleton said: “It’s hard sometimes. I have felt publicly bullied a little bit just by, you know, when I read things that clearly aren’t true or that, whichever way someone looks at it, it’s a negative side.
“It is quite difficult because effectively I’m just trying to live a life like any 30-year-old.”
She added she had to get used to “not being entirely private” and as a result she can never entirely relax.
NBC’s Matt Lauer asked: “The very same media and the very same people on those social media sites that want to make you the IT girl, at some point they decide we’re done and they sometimes want to tear you down. Have you experienced that?” Ms Middleton replied: “Yes, quite a lot actually.”
Her critics have pointed to speculation that she may be offered a job with NBC as a correspondent as a sign she is piggybacking on her sister’s life to enrich herself.
She already writes for the magazine Vanity Fair and has written a book about party planning called Celebrate, although it was ridiculed by reviewers.
In the interview Ms Middleton also opened up about the royal wedding, which she said seemed like a small event to her, even though it was watched by 300 million people around the world.
She said: “It sounds funny to say but we saw it as a family, as just a family wedding.
“I didn’t realise perhaps the scale of it until afterwards. I had to make sure I helped my sister where I could and look after the bridesmaids and page boys.”
She added: “We really saw it as a family getting together and doing their bit like any other family.’
Ms Middleton added that even while walking through Westminster Abbey carrying her sister’s wedding dress train she did not fully grasp the scale of what was happening.
She described the day as “surreal” and told how it was only when she walked out on to the balcony of Buckingham Palace with her sister at her side that she thought: “Wow, this is pretty special”.
Mr Lauer asked Ms Middleton what had happened to her full-length, figure-hugging ivory bridesmaid’s dress.
Ms Middleton said: “I haven’t worn it since. But I think I’ll just keep it there.
“I think it’s the sort of thing that I’m sure I’ll bring out if someone wanted to see it or my children one day want to see it. Then I’ll show them that. It’s tucked away.”
Turning red in the face, she added that for her to get the attention instead of her sister the bride was “flattering, embarrassing”.
Ms Middleton’s dress, which, like the bride’s, was created by Sarah Burton of Alexander McQueen, was highly praised in the media. Made of ivory crepe fabric, it was styled with a cowl at the front and organza-covered buttons at the back.
Copies of the dress were soon available on the high street and sold out within hours.