Dame Jacqueline, the former children's laureate, warned that the preoccupation with uploading photographs to social media channels has led to teenage girls all wanting to look the same.
"Now girls are expected all to have long gorgeous hair, to be relatively willowy," she said. "It's this awful kind of self-consciousness all the time whereas I don't remember worrying all the time about what other people thought of us. There doesn't seem a place for individuality anymore."
She added: "And also with the whole Twitter thing, if you post something that doesn't try and immediately be what is considered valuable, kind and correct you are so hideously...trumped...it just seems sad."
Dame Jacqueline was speaking about how to become a best-selling children's author at the London Book Fair. She said that while girls today face challenges with social media, she praised the positive developments that have changed women's position in society.
"I do think it is wonderful now that girls are expected to achieve and have brilliant careers," she said.
"When I was a girl if you were considered bright there were two occupations - do you want to be a nurse or do you want to be a teacher? Nothing else was ever considered so we have moved forward enormously.
"In many ways it is wonderful how much more open we are as a society and for young people and yet we're also closed because there is just a particular roof that we have to walk on."
Dame Jacqueline, who has written more than 100 books over a 35-year career, has previously spoken about the disruption of modern technology.
Last year she complained that electronic life has "wiped out books", as adults prefer to check their emails and smartphones to picking up a paperback while on the move.
Dame Jacqueline said she finds it "sad" to see adults are not reading as much as they used to, claiming she is often the only one on a train journey now holding a book.
The writer said that while children still have huge appetite for reading, thanks in part to encouragement from their schools, adults increasingly appear to prefer their smartphones.
"I find it sad that adults aren't reading as much," she said. "On the train 10 years ago people were reading books - I would love trying to work out what titles they were reading.
"Now I'll be the only person with a book on my lap and everyone else is glued to their smartphones or checking emails. Electronic life has wiped out books."
Are you a parent in New Zealand? We want to hear from you. Join our parenting group on Facebook.