The British singer, who miscarried her second baby in two years last fall, called Kanye's comments "wrong on so many levels."
Now, Allen is stepping outside Twitter and opening up about her misfortune in a new U.K.-produced documentary called Lily Allen: Riches to Rags, in which she also reveals she suffered from a serious eating disorder and used to purge after meals.
The Channel 4 doc, filmed over seven months from March until October of last year, shows a tearful, vulnerable Allen, who talks about her sadness over losing her second child six months into her pregnancy last year, reports the U.K's Daily Mail.
"It was a really long battle, and I think that kind of thing changes a person," she says in the interview.
The 25-year-old also admits that her incredible weight loss was the result of an eating disorder. "I used to vomit after meals," she said. "It's not something I'm proud of. But, I tell you what, a lot of people came up to me telling me how great I looked and I'd be on the cover of every magazine."
Despite the praise, Allen said she wasn't happy on the inside and finally realized she was "a pop star, not a model."
"I thought I looked good and it was great to be able to try on clothes and feel a million dollars. But I wasn't happy, I really wasn't," she said. "I would love to be the skinniest minniest person in the world but I can't do that without being unhappy. I like food. Don't make me feel s--t for not being really skinny and having an eating disorder."
There is a silver lining to all of Allen's suffering though—she is now engaged to building company owner Sam Cooper, with the two set to wed later this year. The duo have been dating since 2009 and Cooper popped the question last Christmas, a month after they lost their baby.
Allen was back in the spotlight this week after she attended the Chanel show during Paris Fashion Week and visited Karl Lagerfeld's studio. The eccentric designer is making her wedding dress.
The documentary also delves into Allen's love of fashion, and shows her at the Covent Garden vintage boutique store she co-owns with her sister.
Lily Allen: Riches to Rags airs on March 15 in the U.K.