"If you'd told me three years ago, 'Your sister's going to be the winner of The Voice, I'd say, 'Sure, I'd believe it,' " said her brother Mark Grimmie, 21. "I'm done being surprised by cool things she does. She's very talented and she's worked incredibly hard - it's a dangerous combination."
Since belting out "My Heart Will Go On," and "Halo" at the Lenape Performing Arts Center for the "Idol" competition, she's garnered a massive fan following and been dubbed the "Queen of YouTube." It all started with a cover of Miley Cyrus' "Party in the U.S.A." recorded in her Marlton bedroom in August 2009 with a keyboard and a Sonic the Hedgehog poster taped on the wall behind her.
Her videos took off, and have amassed more than 350 million views to date.
At 20, the second-youngest competitor in the finale has also gone on two international tours with Selena Gomez and released two CDs, though she has yet to be signed.
Monday, she competes for Adam Levine's team against country singer Jake Worthington (Team Blake Shelton) and indie rocker Josh Kaufman (Team Usher), for a recording contract and the Season 6 title.
Behind Grimmie's powerhouse vocals and signature choppy-on-the-bottom, poofy-on-the-top hair (she first got the signature cut at Hello, Gorgeous salon in Marlton) is a video-archived history of goofing off with her two best friends in South Jersey.
Sarah Luebkemann, 20, met Grimmie at Bethel Baptist kindergarten in Cherry Hill when the two were 5. "I think she knocked over my crayons or I knocked over hers. We've been best friends ever since," Luebkemann said from her Marlton home.
A YouTube search brings up dozens of videos of the two, along with a third musketeer, Lauren Longo of Cherry Hill, doing improvised skits, songs, and lip-synching performances.
"The first time I heard Christina sing, it was in third grade and it's kind of insane because not only was she a fantastic singer but she could pick out these insane harmonies," Longo, 20, said. "I really think she has perfect pitch, she just hears things. At 8 years old I'm thinking, 'My friend's really, really talented.' "
Grimmie has also spent a lot of time honing her craft. In high school, she'd go straight home after classes and spend hours in her room on the keyboard, which she took up at 10, mostly learning by ear. She also plays flute and bass.
She attended Marlton Middle School and Cherokee High School until sophomore year, when she switched to homeschooling. Her family attended Fellowship Alliance Chapel in Medford before moving to Los Angeles in winter 2012 after Grimmie joined Selena Gomez on tour.
Grimmie's father, Albert, works for Verizon; her mother, Tina, worked as a receptionist before being diagnosed with breast cancer.
In a sobering and sweet moment after her first Voice audition, Grimmie told the judges her mother was her inspiration. "I thought she wouldn't get to see me do anything like this, so, I love my mom and I'm happy I got to do this for her," she said as the camera panned to her mother wiping away tears backstage.
Mark Grimmie says his mother's cancer is still "very month to month. She's in a clinical trial and it's not over, but she's kicking it and she's so, so happy right now."
In the road to the finale, Longo and Luebkemann have flown to Los Angeles several times to visit their friend. Luebkemann returned home for one day to hand in finals at Camden County Community College in Blackwood only to get back on a plane two days later to be in Los Angeles with Longo for the finale.
Longo brought along bath salts and bubbles. "It's part of her ritual. She likes to relax before going on stage," she said.
Last time, Luebkemann went bearing doughnuts. "She's not the most health-conscious person," she said of her svelte friend.
Grimmie tells her friends Los Angeles weather is great but she misses the pizza at Sal's Pizzaworks in Marlton, Wawa, water ice, and the availability of ice cream (L.A. is filled with fro-yo, she laments).
The three besties have days when they get nostalgic for trips to the Ocean City boardwalk, Manco & Manco's pizza and a trip on the "tower ride." "We would just scream at the top of our lungs at whoever was below us as we dropped," Luebkemann said.
At Cherokee High School, hallway signs made by Luebkemann encourage students to vote for Grimmie, and the singer's music plays on the loudspeaker before the start of class.
Donna Charlesworth, principal at Cherokee North, said teachers remember Grimmie as a sweet, quiet girl, never one to share her talent. "Other kids would always ask her to sing or say, 'Hey, have you seen her on YouTube?' and it was amazing to hear that huge voice come out of little Christina."
Charlesworth said the school store was stocked with Grimmie posters.
"There is a tremendous amount of enthusiasm and support for Christina, and the school community takes such pride in that one of their own is given this opportunity," she said.
Ott's Pub in West Berlin will have a viewing party Monday complete with a DJ, Grimmie-specific trivia, prizes, and T-shirts.
"It's really fun having something to root for. It's almost like your team is in the World Series," Longo said.
The Voice has become a reality vocal competition as much about pipes as online presence. Grimmie has both.
Her fans follow her in huge numbers (more than 531,000, on Twitter), and The Voice set a Twitter record last week when her fans had the opportunity to tweet in to save her. "Save Christina" was the No. 1 worldwide trending topic.
Longo said Grimmie did no marketing when she started posting on YouTube. "People just gravitated toward her and shared her because she was good."
Grimmie loves video games - her YouTube username is zeldaxlove64, a nod to the her favorite game ( Zelda) and system (Nintendo 64).
She has a nerdy-chic aesthetic and sense of humor that her friends say attract fans.
"She's very real with her fans she talks about things she loves - she doesn't try to be perfect," Longo said.
On Thursday, Grimmie found time between a packed schedule of media interviews and dance and vocal rehearsals to chronicle, through photos, the rescue mission of a cockroach she named Sebastian.
Added Longo: "I think it's very transparent that she's a cool person who never tried to be anything she wasn't."