Her first book (Girltalk) came out 30 years ago and is still in print (in many languages)!
She comes from a family of writers: her mom was the garden editor of House and Garden magazine, and her dad wrote for radio, TV, and newspapers. She learned not to say "like" and "you know" from her dad; it taught her to care about words.
She even wrote a Dear Carol letter to herself and wrote advice for herself when she wanted to write a novel (after many years of writing nonfiction). She went to therapy to understand why she hadn't challenged herself to write fiction. Took writing classes at the Y in NYC and then finally write her first Melanie Martin book. It was rejected at first, but she kept at it until Knopff accepted it and published the series. She used what she knew (languages and art) in the plot line to differentiate her book from other books.
The Speed of Life (for 7th and 8th graders) is coming out next fall (most likely it'll remain a standalone book).
Why does she use so much word play in her books? When she confided in Elizabeth Winthrop (another author) that her character kept going back to words when she wanted her to think about other things, Winthrop said that Carol should let her character go ahead and be herself (she could edit later).
She can't pick a favorite character, but her favorite book to write was her 'momoir' about being pregnant, which she wrote when she was pregnant.
When she hears kids say that they don't like reading or writing, she likes to add "yet" to the end of the statement. She believes they will find the right genre, and with some extra work, reading and writing will eventually come to them.