She spoke about death in a child’s voice, and people listened.

“I’m Gabriella Miller, I’m 10 years old, and I have brain cancer,” she would begin.

In the final months of her life, Gabriella Miller was a celebrated activist, a charismatic public speaker and an advocate who raised hundreds of thousands of dollars for the Make-A-Wish Foundation and helped launch the Smashing Walnuts Foundation to fund pediatric cancer research.

She was also a kid who wanted to grow up and felt it was unfair that she wouldn’t have the chance. Even as she grieved the loss of her own life, she wanted to help her parents and little brother carry on with theirs. She left them a list of final instructions: When they go to Disney World, they have to ride the Haunted Mansion first, five times. They should go on the cruise they’d originally planned to take as a family of four. They must always have an extra piece of cake for her on birthdays — vanilla with chocolate frosting was her favorite.

Gabriella died at home late Saturday night after an 11-month battle with an inoperable brain tumor.

Gabriella Miller (Family photo)

Her family was surrounded by more than 2,000 people in the packed gymnasium of Heritage High School in Leesburg, Va., on Wednesday night, at a public memorial service for the fifth-grader. She had always loved bright colors, so scores of children lined the hallways of the school with vibrant bouquets of tissue-paper flowers.

Gabriella knew the raw power of her own story could drive home the fact that only about 4 percent of federal funding for cancer research is dedicated to pediatric cancers. In a video projected on the white gym wall, the crowd of mourners listened to Gabriella speak once more of the need to help kids with cancer.

“I need my childhood,” she said. “And you know, less and less kids are going to have their childhood . . . if people don’t raise awareness and raise funds.”

Mark and Ellyn Miller, Gabriella’s parents, listened as their daughter’s educators and friends spoke about the child they loved. Gabriella’s 6-year-old brother, Jake, wriggled tearfully in his seat and leaned heavily against his parents throughout the eulogies.

The headmaster of Gabriella’s school described her trademark giggle: “Delightful, invigorating,” he said. “The sound of her laugh was a Tchaikovsky crescendo.”

Cindy Chambers, who wrote the children’s book “Beamer Learns About Cancer” with Gabriella, recalled a passionate and gifted young writer who penned poems “far beyond her years.”

Gabriella described her feelings about cancer in a poem she wrote in July:

“I closed my eyes & fell asleep. A deep dark sleep. I dreamt of pain, death, loss, anger. I kicked & cried & cursed in my sleep. I tried to wake up. I closed my eyes. I opened them. I would not wake up. No, but I was awake. Wide awake. I was living the dream. The nightmare.”

She also wrote poems with her friend Tom “Tattoo Tom” Mitchell, who founded Stillbrave Childhood Cancer Foundation after his own teenage daughter died of the illness. He spoke Wednesday about the comfort of Gabriella’s presence at a memorial service they both attended earlier this year, for another child who had died of cancer.

“At one point when it was more than I could bear, and I wanted to get up and run out . . . Gabriella intuitively reached over and took my hand in hers and put her head on my shoulder,” Mitchell said. “I haven’t been the same since. If I do nothing greater the rest of my life than to have been loved by that little girl, I will consider this life to have been a very successful one.”

Gabriella entered hospice care at home last week after a sudden and sharp decline in her health.

“Am I going to make it?” she asked her parents the night before she died. When she understood that she wasn’t, her mother said Gabriella pushed her favorite stuffed animal — the one that had helped her feel better when she was sick — into her mother’s hands, to help ease the pain. Gabriella kept adding to her list of parting instructions for as long as she could communicate; after she lost the ability to talk, she signed letters with her hand.

Her most important edict is immortalized on video, part of an interview for a childhood cancer awareness documentary. In the footage, she sits cross-legged on her bed, wearing a yellow shirt and a resolute expression framed by sparse wisps of dark hair. Gabriella’s right eye levels a steady gaze at the camera; her left is turned inward, yielding to the mounting pressure of a growing tumor.

“If I go, if I lose my battle, then I want other people to carry on with the war,” Gabriella says firmly, waving a small fist to emphasize her point. “They’re going to win this war.”

Then she pauses and looks down. When she speaks again, her fragile voice is the sound of a scared child who is trying to be brave.

“And I’ll be with my friends,” she says. “I’ll be in a good place, and it won’t be all that bad.”