Rosie the doll does everything with her look-alike owner, Marley Darrington.
The pair cuddle in bed at night, they go to grandma's house and, now, Rosie gets to experience what it's like to walk in 5-year-old Marley's shoes.
On Friday, Rosie received a pair of leg braces one-tenth the size of those that Marley wears so she can be just like her.
"We've had a hard time getting Marley to wear her braces, so we're hoping this will help," said Martha Snipes, Marley's grandmother.
Marley was born with club feet and has had two surgeries and two pair of braces.
Five students in the advanced computer-aided drafting and design class at Mesa Ridge High School, where Snipes works as an educational assistant, spent two months designing and making the doll braces using a 3-D printer.
The students met Marley and Rosie for the first time Friday, when they presented them with small rainbow-colored braces exactly like Marley's first pair of braces.
Marley clutched her constant companion cheek-to-cheek, waved one of the doll's arm and said, "Thank you" in a shy but appreciative voice. "It makes Rosie happy."
Marley doesn't really like her braces, her grandmother says, but Rosie just might provide the right motivation.
"We're thinking she'll be more accepting of wearing the braces if her doll had braces, too," Snipes said.
Marley attends Head Start, a federal program for preschoolers from low-income households. That's the only place she can't take Rosie because toys aren't allowed at school, Marley said.
The high school students were excited about being able to apply what they're learning in science, technology, engineering and math tracks to making something useful, said teacher Nathaniel Sobin.
"My first thought was this is a great project because it has actual application and benefits a real person," he said.
Knowing they were helping someone and making a difference in someone's life made the project more interesting than typical classroom assignments, said Seth Duran, a junior.
"It makes me feel like I'm actually doing something good," senior Zachary West said.
It took six attempts for the students to figure out the right formula for making the doll braces. They finally abandoned a hard plastic for a more flexible material.
"It was a grueling process," Zachary said. "We had to keep tearing it down because we kept messing up."
"We had no idea what we were doing," Seth said.
Students are working on a second pair of braces for the doll that will match Marley's current braces, which have Tweety Bird images. So both doll and girl will have two pairs.
"It's a great experience to impact someone's life and help her feel accepted," said Real Williams, a junior.
Marley let go of Rosie long enough to place her on the floor and let her try out her new braces.
"The braces will help her walk," Marley said, coaxing her doll to take a few steps.
"They even fit," said her grandma, smiling.