Betancourt was born and raised in rural Vermont. She lived across from a dairy farm; this rural setting would later influence many of her works. During her childhood, she never considered being an author. Instead, she wanted to dance, and studied tap dancing. When she grew too tall (at five feet, eight inches) to be a Rockette, she decided to become a nun in her junior year of high school. After graduating high school, she moved to Rutland, Vermont where she entered the Sisters of Saint Joseph, a teaching order of nuns.
She earned a Bachelor of Science in 1964 from the College of St. Joseph the Provider and a Master of Arts degree in film from New York University in 1974.Women in Focus, her first published work, focuses on her master's degree project.
Betancourt moved to New York City, where she taught public high school. Betancourt also married and had a daughter, Nicole. She wrote her first children's book, SMILE! How to cope with braces, in 1982 when her daughter Nicole has braces, and soon became a full time author. She later divorced.
She currently lives either on the top floor of a sixteen-story building near the American Museum of Natural History in New York City or in her home in Connecticut. In her free time she draws, oil paints, gardens, and reads.
In television, Betancourt has garnered the National Psychological Award for Excellence in the Media, two Humanitas Awards, and six Emmy Award nominations.
Betancourt has also won numerous awards for her novels, including a Children's Choice Award from the International Reading Association and the Children's Book Council for Sweet Sixteen and Never... and a Lifetime Achievement Award.