WASHINGTON - A former friend and adviser of Melania Trump says it was the worst mistake of her life to work for U-S President Donald Trump and his family.

She's lashing out at the first lady for not defending her over questions about costs for the presidential inauguration she helped produce.

Stephanie Winston Wolkoff was an unpaid White House adviser to the first lady until February 2018, when her contract was terminated as questions about inaugural spending arose.

In “Melania and Me: The Rise and Fall of My Friendship with the First Lady,” Wolkoff writes that when it really counted, Melania wasn't there for her.

She goes on to say “She wasn't really my friend. In fact, I wish I had never met her.”

Wolkoff, a New York-based event planner, says the pair first met in 2003 in the hallways of Vogue magazine, where Wolkoff worked.

Stephanie Grisham, a spokesperson for Mrs. Trump, blasted the book in an emailed statement as “full of mistruths and paranoia” based on an “imagined need for revenge.”

Wolkoff also writes about frostiness in the relationship between the first lady and the president's eldest daughter, Ivanka Trump.

She said she and the first lady both once “bellied over with laughter” after Mrs. Trump referred to Ivanka Trump - long seen as her father's favourite child - as “Princess.”

Wolkoff also detailed how they launched “Operation Block Ivanka” to keep her from being too prominently featured in inauguration day photographs of her father being sworn in to office.

Ivanka Trump has declined comment on the book.