(CNN) -- Actress Lena Dunham canceled several appearances to promote her new book after a self-described "rage spiral" over allegations that she molested her sister as a child.

The allegations stem from passages in Dunham's collection of personal essays, "Not That Kind of Girl," in which she describes sexually experimenting with her younger sister as a child. In one essay, she describes bribing her sister with three pieces of candy to kiss her on the lips for five seconds. She also describes probing her 1-year-old sister's vagina when she was 7 out of curiosity over how it compared to hers.

"One day, as I sat in our driveway in Long island playing blocks and buckets, my curiosity got the better of me. Grace was sitting up, babbling and smiling, and I leaned down between her legs and carefully spread open her vagina," she writes in the book.

Kevin D. Williamson -- known for taking hard-right positions that stir controversy -- seized upon the passages in a column for conservative publication National Review.

Specifically, he accused Dunham's parents of enabling "disturbing behavior that would be considered child abuse in many jurisdictions ... sexual abuse, specifically, of her younger sister, Grace, the sort of thing that gets children taken away from nonmillionaire families without Andover pedigrees and Manhattanite social connections."

Truth Revolt's Ben Shapiro picked up the torch, calling the book passage "disturbing."

Dunham, creator and star of the popular HBO show "Girls," said she was "dismayed" over the interpretation of events described in her book. In a statement to Time magazine, she said she does not condone "any kind of abuse under any circumstances."

"Childhood sexual abuse is a life-shattering event for so many, and I have been vocal about the rights of survivors. If the situations described in my book have been painful or triggering for people to read, I am sorry, as that was never my intention."

Referring to her sister, she said, "anything I have written about her has been published with her approval."

Over the weekend, Dunham fired back on Twitter, where she has 1.8 million followers, calling the allegations "upsetting and disgusting."

Usually, "this is stuff I can ignore," she said, "... but don't demean sufferers, don't twist my words, back the f**k up bros."

Dunham then apologized on Twitter for canceling book tour appearances scheduled for this week in Berlin and Antwerp, Belgium.

It was not clear Monday whether the cancellations were related to the recent allegations. Messages sent to Random House, Dunham's publisher, and her publicist were not immediately returned.

Truth Revolt claims it received a "cease and desist" letter threatening legal action if the publication did not remove an article it published last week about Dunham.

Dunham's sister, Grace Dunham, did not respond to requests for comment. Amid growing controversy Monday, however, she tweeted, "2day, like every other day, is a good day to think about how we police the sexualities of young women, queer, and trans people."