Then she phoned her mother.
"I did it, Mom!" the 58-year-old Patchogue resident said.
For Hannigan, a former sergeant who helped care for wounded soldiers during the Vietnam War, finishing the mile walk upright was a milestone she never expected to achieve.
Just two years ago, she was told she'd never walk again -- after an autoimmune disease left her paralyzed. But then last year, she was invited to participate in a clinical study, where she could wear electronically-powered leg attachments and relearn how to walk.
She trained with physicians at a Veterans Affairs center in the Bronx, taking her first steps, gaining stamina.
Saturday, she took her biggest stride yet, using her bionic legs to cover a mile-long stretch of the Sunrise Highway, where hundreds gathered to watch Hannigan and others compete to raise money for wounded veterans and families of fallen soldiers.
When she lost the use of her legs, Hannigan said, the future looked so bleak. "You can't possibly imagine how you're going to live your life again; how you're going to live a normal life again," she said.
Her high-tech ReWalk exoskeleton, manufactured by Argo Medical Technologies, has restored some of her independence. She said she can now tell her family, "No, no, no. I can do this myself now."
Robert Woo, 44, a Manhattan architect, also participated in the race using ReWalk. Paralyzed from the waist down in a construction accident five years ago, Woo set a personal best for distance Saturday.
"It's so difficult to describe what its like being able to stand up, considering you're in a chair for five years," he said.
The charity foundation Run for the Warriors hosted the race, as well as 5k and 10k competitions. The event raised about $100,000, the organization said.
Hannigan began the second half of the race by taking a call from her 80-year-old mother, who was too sick to attend.
"I made it halfway, Mom," Hannigan said, fighting back tears. "I'm doing great!"
Minutes later, she told a group cheering her on, "My mom said when I was paralyzed -- and I didn't want to hear it -- that 'when God closes doors, he opens others.'