Gabriella Miller can smile again.

The precocious 10-year-old, who was named Loudoun County’s Volunteer of the Year at a county ceremony May 1, has an inoperable brain tumor. A few months ago, it pressed against nerves, blurring her vision and causing a slight palsy on one side of her face, making it difficult for her to smile.

Now, the tumor is shrinking. Gabriella can see clearly, and when she stood before a crowd that rose to a standing ovation in the county supervisors’ boardroom, she grinned happily as she took the microphone.

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

Gabriella, a fourth-grade student at Loudoun Country Day School, was recognized for leading a letter-writing campaign that helped raise more than $275,000 for the Make-A-Wish Foundation last year.

She told the audience that she has been a dedicated advocate for fighting childhood cancer ever since her diagnosis. She has also been an unrelenting optimist: “You might have a bad day today, but there’s always a bright star to look forward to tomorrow,” she said.

Soon after Gabriella’s tumor was diagnosed in November, she submitted a request to the Make-A-Wish Foundation for a trip to Paris. But she also wanted to make sure that other children would have the same opportunity to have their wishes granted, her mother, Ellyn Miller, said.

So Gabriella and her family decided to help the Make-A-Wish Foundation secure a $1 million donation from Macy’s, a contribution that was promised if the company received 1 million letters to Santa Claus before Christmas. With the help of a Facebook campaign that was launched Dec. 1, Gabriella’s letter-writing drive quickly took off: tens of thousands of letters streamed in during the first two weeks, and word of her efforts went viral.

The Millers’ synagogue — along with interfaith groups and churches, friends, family members, celebrities and others across the nation and around the world — joined in, and two days before Christmas, Gabriella delivered nearly 241,000 letters to her local Macy’s store. Including letters sent in separately on her behalf, the total surpassed 250,000, Miller said.

The successful campaign showed Gabriella how powerful her message could be. With that in mind, she and her family plan to launch a new foundation to raise money for pediatric cancer research, called the Smashing Walnuts Foundation. When Gabriella was first told that her tumor was about the size of a walnut, her family members began a ritual of smashing walnuts on the rails of the family’s deck to help Gabriella visualize winning her battle against the disease.

The positive energy, along with Gabriella’s oral chemotherapy regimen, seems to be helping, her mother said. The tumor is smaller, and since ending her radiation treatment in January, Gabriella has more energy.

The family hopes their planned foundation will help other young cancer patients and provide funding for much-needed research.

Less than 4 percent of the federal funding budgeted for cancer research is devoted to pediatric cancer research, Gabriella’s mother said. “And that’s for all pediatric cancers. It’s a drop in the bucket; it’s nothing. And unfortunately, in these times, you can’t just ask for more money. So the goal of the foundation will be to raise awareness of pediatric cancer and also to raise money for research,” she said.

They plan to dive into the plans for the foundation as soon as they get back from their much-anticipated vacation. The family will head to Paris on Friday for Gabriella’s Make-A-Wish trip. Miller said her daughter grows more excited by the day.

“She heard someone say that you can take a bullet train from Paris to London, so she’s got it in her head that she wants to go to London now,” Miller said. “She wants to have dinner at the Eiffel Tower. She wants to have escargot. She cracks me up.”

Gabriella can’t wait to get onto the plane, Miller said. But first, there’s one thing left to do.

On Wednesday, two days before the Millers head to France, Gabriella plans to cut her long, dark hair and donate it to Locks of Love, a group that provides hairpieces to children who have suffered medical hair loss.

Gabriella lost some of her hair on the lower part of her head during her radiation treatment, Miller said. But that didn’t stop her from wanting to share what she has left.

“This is a little girl who is bald from the ears down, but she still has long hair on top,” Miller said. “And she wants to cut it and donate it, to help other kids.”