The monarch butterfly will be renamed the Catherine butterfly in honor of a Sandy Hook victim on Saturday, what would have been a milestone for the animal-loving girl.

“It's Catherine's birthday. She, this year, would be 18,” said Jenny Hubbard, Catherine Hubbard’s mom. “If I had to sum up June 8—it’s just celebratory. It's the day she was born. It's the day she graced this earth. Why wouldn't it be a celebration?”

Catherine will forever be six years old. The little girl with fiery hair and matching passion for all creatures died on Dec. 14, 2012, but her birthday is still marked with an annual party.

“I could easily go down the rabbit hole of, ‘What have I missed? And what are the milestones?’ This year would be her 18th birthday. She'd be graduating from high school. She'd be heading off to school. And all of those thoughts—I can ponder them, but they always lead me back to this place that she's gone. I’d much rather focus on what I had when she was here with me. I had six full years, so it’s a conscious choice I make, a lot of times, day in and day out,” Hubbard explained.

She told News 12 that the first year after Catherine’s death, their family marked it privately doing something she loved, but it didn’t feel right. Birthdays in the Hubbard family had always meant big parties in the backyard with a theme, handmade invitations and games.

“We needed to honor her spirit with a birthday party of some sort,” Hubbard recalled thinking.

She wanted to mark the day in a similar way to how they used to. Before Catherine’s death, she always asked for an “all animals” birthday party, which Hubbard would get her to narrow down. One year, there was a horse party. Another year was a butterfly party.

“I'll never forget it, and it was probably the one where I looked at her and realized that this is her. She was in such her element and so peaceful and so joyful,” Hubbard said.

So, every year, the Catherine Violet Hubbard Animal Sanctuary in Newtown hosts Catherine’s Butterfly Party, a free family-friendly celebration for the community that doubles as a pet adoption event. There are games, face-painting, crafts, animal ambassador exhibits, educational events, K9 demonstrations and dozens of rescue groups with hundreds of pets who need a good home. The first year drew 1,500 people.

“We were floored. I was so excited to be able to share Catherine's spirit, her love and give her the ‘all the animals’ party she always begged for,” Hubbard recalled.

The party has continued year after year, continually growing. Last year, 12,000 people showed up.

“You arrive at the event green, and you look left, and you look right, and there's families and people of all ages just celebrating the wonder and awe that's animals,” said Hubbard.

This year there's another element. The North American Butterfly Association will rename the monarch butterfly the ‘Catherine butterfly’ for one day to honor Catherine’s enduring kindness on what would have been her 18th birthday. Butterflies were one of Catherine's favorite creatures.

"We could not be more excited to partner with the Catherine Violet Hubbard Animal Sanctuary in honor of Catherine's birthday and to continue our efforts to protect monarchs, and all butterflies and their habitats,” said Dr. Jeffrey Glassberg, found and president of NABA. “Throughout human history, many peoples have believed that butterflies are the repositories of human souls. How fitting it is then, that we continue Catherine's work of showing kindness toward animals, including butterflies, reminding everyone that if we can save butterflies, we can save ourselves."

The CVH Animal Sanctuary was created in 2013 to commemorate and honor Catherine’s life. It sits on 34 acres and includes a NABA Certified Monarch Garden, committed to creating, conserving and protecting monarch habitats.

Catherine’s Butterfly Party will be held June 8 at the Fairfield Hills Campus in Newtown from 12 p.m. to 4 p.m. You can learn more about the event, along with the sanctuary’s mission and programs, at the nonprofit’s website.