When the final installment of the “Twilight” movie series premiered last month, one cast member wasn’t even allowed to watch it.

The hands of Isabelle McCall, a pianist and Runnels Junior High student, are featured prominently in the popular film when Renesmee, the young daughter of main characters Bella and Edward, plays a piano duet with her on-screen father.

Hired as a musical stand-in for actress Mackenzie Foy, Isabelle’s hands flitter across the keyboard for a few seconds while she performs the lullaby.

But at 12 years old, Isabelle might not see the PG-13 film for a while.

“Maybe when she’s 14 or 15,” her father, Tony McCall said from their Prairieville home. “It depends on whether she figures out the code for the satellite.”

An intelligent, focused youth, Isabelle began playing piano at 3 — playing was a dream of her mother’s, who didn’t have the opportunity as a child — then took up acting at 8.

“When she was in my tummy I listened to music,” said her mother, Sichin Li-McCall. “She was surrounded by music from the moment she was there.”

Isabelle decided to start acting because she thought she was too shy and set out to change. Acting helped her learn to talk to new kids at school and step out of her shell, she said. She loves stepping into another persona, trying to understand what the character thinks and feels.

“I like that you can be a different person,” she said. “You don’t have to be who you are.”

At 8, when she started acting, Isabelle played a princess in Baton Rouge Little Theater’s production of “The King and I.” Since then she has played the lead role of Wilbur in her school’s production of “Charlotte’s Web,” performed with Opera Louisiane and appeared in small roles in two television pilots.

Her Hollywood experience came almost two years ago in February 2011 after the McCalls learned from a friend that the producers of “The Twilight Saga: Breaking Dawn — Part 2” needed a child actress to stand in for Foy. Sichin Li-McCall sent the casting director a video of Isabelle — then 10 years old — playing piano, and she was offered the part.

On set at Celtic Media Centre, Isabelle had her own trailer with a star on the front that read “Child Pianist.” The crew nicknamed her “The Prodigy.”

Isabelle was far from star-struck being around teen idols Robert Pattinson, who plays Edward Cullen, the vampire, and Taylor Lautner, known for portraying Jacob Black, a shape-shifting werewolf. She didn’t even know who they were.

The night before her first day on the set, Isabelle and her mother sat down at the computer to go over who the actors were and what they looked like.

“It was good that she was not aware of all these actors, because she was not nervous,” said Sichin Li-McCall. “To her, it was just playing the piano, and she was used to that.”

Two things did impress her: The buffet of food a chef prepared for the crew and the “adorable” dog Lautner walked around the set.

Named “Renesmee’s Lullaby,” the song she had to learn and perform was just two pages long and did not present a challenge, Isabelle said. However, she received changes to the tune “three or four” times over the course of filming.

During filming, she reported to a huge soundstage complete with an interior reproduction of the house used in the film, half finished, “like a doll house,” Isabelle said.

On the piano bench, Isabelle sat next to Pattinson, who plays Renesmee’s father, as he began to play a tune on the piano. Joining him, they played what is portrayed in the movie as an impromptu duet that displays the prodigious talents of Renesmee, who is a vampire-human hybrid.

For Isabelle, the most difficult part involved playing while a camera filmed from directly above her head. She had to stretch her arms as far as possible to reach the keys and continue playing.

“It was hard,” she said in a matter-of-fact shrug. “My arms were short. I was 10.”

The three days of filming appeared as just seconds on the screen.

“They keep adding another layer, every time they bring another person in and another person,” said her father, Tony McCall. “They do the same thing over and over. It was neat to watch the process.”

Until November the McCalls could not talk about their experience. They had to sign confidentiality agreements, which a public relations specialist reminded them of constantly.

Isabelle’s friends were not too impressed, she said, but some other girls who have crushes on the “Twilight” actors have shrieked over how close she sat to their idols.

For the future, Isabelle hopes to keep acting, she said, for a hobby.

Nine years ago, while her Po Po — a Chinese nickname for a grandmother — battled cancer, Isabelle would do all the things she saw the doctors and nurses do during Po Po’s doctor visits. Her grandmother called Isabelle “my little doctor,” Sichin Li-McCall said.

That was when Isabelle announced she would become a doctor, and she has not relented.

“I guess it’s because I really want to help people,” she said. “It’s just interesting.”