She grew up in Mount Kisco, New York with three sisters and a brother. She graduated from Yale University and has a Master’s of Education degree from Harvard University. Since 1985 she has lived in Silver Spring, Maryland. Her husband teaches history at Montgomery College. She has been a writer for reading textbooks for three decades.
Tripp is best known for her work with the American Girl series. She wrote all the books in the Felicity, Josefina, Kit, and Molly series, and three of the books in the Samantha series. She has also written four of the five "Best Friends" character stories to date. Film dramatizations of the lives of Samantha, Felicity, Molly, and Kit have been based on her stories to varying extents.