Her childhood was spent on Long Island and in and around New York City. She enjoyed theatre, literature, and art in high school and college. She graduated from Nassau Community College in 1975 and the Binghamton University in 1977. Following college, she worked as an editor of teen magazines at Starlog Press before starting her writing career. She has been an editor at Scholastic, Inc. She has taught expository, children's, and business writing at New York University and City College of New York. She has a Masters of Science in teaching adolescents from Pace University.

Weyn has written several novel series for teenage girls, and numerous film novelizations. She has written three original fairy tale retellings in the Once Upon a Time from Simon and Schuster: The Night Dance: a Retelling of The Twelve Dancing Princesses, Water Song: A Retelling of The Frog Prince, and The Crimson Thread: A Retelling of Rumplestiltskin.

Her parents are Theodore and Jacqueline Weyn, respectively a pharmacist and artist. She married William Gonzalez on May 15, 1986 and they have two daughters. She is a member of the Fourth Unitarian-Universalist Fellowship of New York.

• Return to Cybertron, 1984
• The Revenge of the Decepticons, 1984
• The Day the Frogs Came to Lunch, 1988
• Love Song, 1988
• Little Women Diary, 1988
• Into the Dream, 1989
• All Alone in the Eighth Grade, 1992
• Elliot's Ghost, 1993
• My Brother, the Ghost, 1994
• Jeepers Creepers (House of Horrors 3)
• Catch That Kid, 2004 (film novelization)
• Mission without Permission, 2004
• The Renaissance Kids, 2004
• The Museum Chase, 2004
• Sleepover, 2004 (film novelization)
• An Amazing Journey, 2005
• The Night Dance: a Retelling of The Twelve Dancing Princesses, 2005
• South Beach Sizzle, with Diana Gonzalez, 2005
• Water Song: A Retelling of The Frog Prince, 2006
• Snowflake, 2006
• Gracie, 2007 (film novelization)
• Mr. Magorium's Wonder Emporium, 2007 (film novelization)
• Reincarnation, 2008
• The Crimson Thread: A Retelling of Rumpelstiltskin, 2008
• Indiana Jones and the Temple of Doom, 2008 (juvenile film novelization)
• The Diamond Secret: A Retelling of Anastasia, 2009
• Distant Waves: A Novel of the Titanic, 2009, Scholastic Press, ISBN 978-0-545-08572-1
• Empty, 2010 (forthcoming)

"Makeover" series

• The Makeover Club, 1986
• The Makeover Summer, 1988
• The Makeover Campaign, 1990

"No Way Ballet" series

Series illustrated by Joel Iskowitz

• Stepping Out, 1990
• A Twist of Fate, 1990
• Emma's Turn, 1990
• Stage Fright, 1990
• Pointing toward Trouble, 1990
• Three for the Show, 1990

"Sitting Pretty" series

• Checking In, 1990
• True Blue, 1991
• Star Magic, 1991
• Liza's Lucky Break, 1991
• A Chance for Chris, 1991
• Boy Trouble, Troll Associates 1991

"Cover Kids" series

• Nicole's Chance, 1994
• Tracey's Tough Choice, 1994
• Ashley's Big Mistake, 1994
• Chloe Mania!, 1994

=== "

"Scooby-Doo" series

• Scooby-Doo! and You: The Case of the Batty Vampire, 2001
• Scooby-Doo, 2002 (film novelization based on a screenplay by James Gunn)
• Scooby-Doo's Super Case Book, with Vickie Erwin, 2002
• Scooby-Doo and the Dance Club Curse, 2003
• Scooby-Doo's Super Case Book II, 2004
• Scooby-Doo and the Loch Ness Monster, 2004 (film novelization based on a script by Douglas Wood)
• Scooby-Doo 2: Monsters Unleashed, 2004 (film novelization)