Diaz's mother Cindy first posted her daughter's story on the ABC7 Facebook page. When Eyewitness News caught up with her last week, she'd received about 300 cards.
After the story aired, thousands of cards flooded in from around the world to celebrate Diaz's birthday.
"Thank you!" said Diaz, who has Down syndrome.
The West Covina Police Department held a card drive at a local mall and delivered the cards in person. Actress Elle Fanning sent a signed doll from Maleficient.
Elementary schools from Hesperia to Bellflower made Diaz cards by hand!
"She really wanted a lot of cards, so I just wanted to make some!" Bellflower resident Mariah Obando said.
Clients at the Orange County Adult Achievement Center helped put her over the top, creating about 320 handmade cards.
"The clients rallied around this and said, 'We want to do this because we're part of this as well,'" said Dave Kooi, vice president of marketing at Orange County Adult Achievement Center.
"It's about being creative!" Brea resident Leslie Ellingson said.
Mother Cindy Diaz was overwhelmed by the response.
"I've cried many times that it's really touched people's hearts," Cindy Diaz said.
For Ashley Diaz, her smile said it all. It was her happiest birthday yet.