Her mother then detailed what she described as a "practical but unconventional and controversial" decision to put her on a restrictive diet.
In one incident, Dara-Lynn deprived Betty of dinner after discovering she'd been fed "700-800 extra calories" during a French Heritage Day festival at school.
"I knew she had ingested more than enough food to make it through the rest of the day. A child who eats 700-800 extra calories at lunch is not going to starve to death if she does not get dinner," Dara-Lynn wrote.
She also halved all of Betty's dinners, and banned her from ever having dessert. In one instance at a Starbucks she threw her drink in the bin after the server added cream to her drink.
After Betty lost 7.2kg over the year, her mother said the "struggle is obviously not over. I don't think it will ever be for either of us.
"[Betty] understands that, just as some kids have asthma, her weight is something she may always have to think about, unfair as it seems."
Betty's concerns about weight a 'constant struggle'
Betty, now 17, said worrying about her weight remains a "constant struggle". She said her mother has since reflected she may have made her lose "too much".
The teen, who has been accepted to Yale, said she feels guilt that her "confidence hinges so much" on how her body looks and feels, and that she feels better when she's "smaller".
She added as she grew up, kids at her school, Hunter College Campus Schools for gifted and talented girls, were "vicious" and the Vogue article "didn't help".
She recalled a day her "best friend" called her a "fat pig" — an incident which left her "devastated".
She said that as a child, the Vogue photo shoot had been a "fun, glamorous" experience but she soon became overwhelmed with the attention on her body.
She said one day a "distant family friend called me "beautiful", I burst into tears. It was too much attention on my body, my appearance."
She said she "never doubted my mom's good intentions with either the article, the book or the diet itself.
"And I did lose 16 pounds in the following year [after starting the diet] because of this healthier eating plan – even though I think a fixation with numbers is generally unhelpful when talking about weight."
Mum said she didn't 'embarrass' her daughter
In an interview at the time of the release of her book, Heavy, Dara-Lynn said her main concern had been her daughter's health — and she acted after receiving advice from her doctor.
She told Anderson Cooper she didn't feel the experience was "embarrassing" for her daughter, and said she'd make deals with her not to eat certain things at public events.
"We would have talked in advance that she was gonna have a piece of pizza and cake like every other kid.
"If she approached the dessert table and was suddenly grabbing for a cookie, I would say, 'Excuse me, we discussed this. You've had your cake, you can't have another cookie.'"
She said this was interpreted as "embarrassing" her child and she felt it was "unfair".
