"Lady Gaga's fans are the worst," she said. "They've said I should kill myself, that they hope I get raped. I mean, it's crazy but I've had this all my life and I just try and ignore it."
Kelly incurred the wrath of some of Gaga's fans when she made catty comments about the singer on her US fashion TV show last year - including calling the pop star "disrespectful" for not walking the 2012 Grammy Red Carpet, and also having a pop at her much talked-about weight gain.
Gaga, who is the founder of the Born This Way Foundation against bullying, took Kelly to task in her open letter, accusing her of being a bully who has chosen a "less compassionate path" by being part of a show that "breeds negativity".
"While I wish you had reached out to me personally, as the head of the Born This Way foundation with my mother Cynthia, we would like to respond," Gaga wrote. "Everyday, through my music and public voice I choose to be positive and work towards a kinder and braver world with our community of followers."
She continued: "I have empathy for you Kelly, but I feel it culturally important to note that you have chosen a less compassionate path. Your work on E! with the Fashion Police is rooted in criticism, judgment, and rating people's beauty against one another.
"'Appearance' is the most used reason for bullying in the world. Your show breeds negativity, and over the years has even become comedic in nature. It glorifies you and Joan Rivers pointing in the camera, laughing, and making jokes about artists and celebrities as if we are zoo animals. What about your body revolution?"
Sharon then got into the mix, and launched a scathing attack on Gaga, branding her a "hypocrite" and a "bully".
"You know it would have been much more dignified of you to do this privately," Mama Osbourne wrote. "I am calling you a bully because you have 32 million followers hanging on your every word and you are criticising Kelly in your open letter. Are you so desperate that you needed to make this public?"
But that didn't end it.
Gaga responded again to Sharon's comments on Facebook.
"The 'real world' can be cruel, why not try to change it into a better place?," wrote Gaga on Saturday. "I am an activist. Nobody takes adolescents seriously, I do. My letter to Kelly Osbourne was open, because her statements on cyber-bullying were public & as a youth activist I'm compelled to be involved."
'I LOVE LADY GAGA!'
Kelly later appeared to be calling a truce, when she told People that she's a big fan of the singer.
"All I have to say on this subject is that I love Lady Gaga!" she said. "I made stupid mistakes when I was 25, as well, when I accused people of doing things that were wrong. We all live and we learn, and like I said, I'm a big fan of hers."
Asked what she thought of her mother coming to her defence, she said: "I have no control over my mother. She can do whatever she wants."
Sharon continued her war of words with Gaga by firing back at the singer via her TV show The Talk yesterday, E! News reports.
Suggesting that one of Gaga's 'Little Monsters' "could quite easily pick up a gun and kill somebody, namely they said my daughter," she explained that she had approached Gaga's manager "because this time, they [the fans] brought my son into it and they said that my son didn't have MS, that he was just a retard. And I should die, my husband should die, we should all die in a car crash."
She continued: "My opinion is, Gaga wants a kinder world. Don't let your fans be so hideously damaging, hurtful, violent, spread violence on your website. If you are a Mother Monster, monitor it.
"She has a huge group of people that work for her that monitor her website. Why haven't you, as a responsible young woman, said 'No violence on my website, no violence, no threats, no violence.'
Sharon then criticised Gaga for her on-stage costume choices, and accused her of promoting guns.
"However, everything is guns, guns, guns...Cut to her first performance on this new tour. She's wearing two guns coming out of her breasts. Now, on her website, if anybody had the time to pick out how many times guns, guns, guns were mentioned, this is not right and she should be stopped."
Sharon added: "All I'm asking her to do is to say, stay true to her foundation, which she said she wants the world to be a braver, kinder world. Don't wear guns, don't allow your fans to use the word guns on your website, on your Twitter. Don't do it. Have it stopped. One word from her, they will stop...
"One young person that wants attention. One person that wants attention, it takes nothing for this to happen. Over her not wanting to lean out to her little monsters to say, 'Hey guys, I love you, I understand you, not everyone does. Please don't be violent on my site,' because it reflects badly on her."
Check out video of Sharon addressing her feud with Gaga on The View here.
Your move, Gaga.
FAST GOSSIP
And finally...
* Zack Snyder directing a new Star Wars film? Not so fast...
* Pregnant Kim Kardashian talks due date and marrying Kanye West.
* "I'm old enough to be her father" - Bradley Cooper, 38, denies he's dating Jennifer Lawrence, 22.
* Ryan Gosling's perfect day would be spent...knitting.
* Why Britney Spears and Jason Trawick took a sleigh ride to splitsville.
* Hulk Hogan suing spine surgery clinic for a cool $50m.
* Another one bites the dust: Lindsay Lohan fires her lawyer.
* Quentin Tarantino drops N-word backstage at Golden Globes.
* Russell Crowe and Dita von Teese secretly hooking up? Total tosh, says the Gladiator star.
* "We're just friends" - Carmen Electra denies dating Simon Cowell.
* Anne Hathaway to star in new Taming of the Shrew film adaptation.
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