BOSTON (CBS) — Proving that a pet can make all the difference in a person’s life, a local woman’s story has turned into a holiday surprise for a dog adoption center.

Darlene McCarthy has multiple sclerosis (MS). When she was diagnosed a few years ago, she was in a bad place. “I didn’t want to do anything. It was a lot to take,” She said.

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MS is a disabling disease of the central nervous system. “When somebody says you have this illness, and now it effecting your balance and your walking, that effects everything,” McCarthy said.

Her doctor told her she needed to exercise. “One day he said as a joke, ‘Maybe you should get a dog,'” McCarthy said.

That’s when McCarthy adopted Beau from Last Hope K9 Rescue, a Boston based non-profit that rescues dogs that would otherwise be euthanized. Beau gave her a reason to get up and get moving.

Walking the dog was the workout she needed. Beau became her therapist. “My balance is a million times better from walking with Beau,” McCarthy said.

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Darlene McCarthy and her dog Beau. (WBZ-TV)

Friday, McCarthy paid it forward. An essay she wrote to the Petco Foundation about how Beau has changed her life was chosen as a winner in that company’s Holiday Wishes program. That means Last Hope is getting a $5,000 grant–a big deal for an all volunteer organization.

“It can cover 50 spay or neuter surgeries. It can pay for heart worm treatments for 10 dogs. I mean, it’s pretty significant,” said Kelli Leahy, director of Last Hope.

“Beau is the star of the day, and he has helped his mom get through some of the multiple sclerosis symptoms she has,” said Christina Brown, manager of the Petco shop in Allston where today’s check reveal took place.

“He was on death row,” McCarthy said. ‘And I know everyone says, ‘oh you rescued a dog,’ and it sounds ridiculous, but when they say who rescued who, it’s a 100% true, they rescue their owners.”

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The Petco Foundation is donating $875,000 to pet adoption organizations this year as part of the Holiday Wishes Program.