05/01/2014 at 02:00 PM EDT
Late last year, Christy Harding was scrolling through her news feed on Facebook when a photo a friend shared
caught her eye.
It was of a little girl named Arianne Moore, 2, who needed a kidney transplant or she'd die. Moore suffers from a rare genetic disorder that causes scarring of the kidney and is on dialysis for 10 hours a day.
"Her page said if your blood type is O you may be able to help," Harding, 37, of Jacksonville, Fla., tells PEOPLE. "I'm type O."
After talking it over with her husband, Harding decided to see if she'd be a match.
"I have a 2-year-old daughter and that's probably one of the biggest reasons," Harding tells Minneapolis-St. Paul's KMSP
"When my husband and I were talking, we knew that if it were her, we would want everyone in the world to try to save her," Harding says.
She turned out to be a match and on May 7, Arianna will have the surgery.
When Harding got the news, she reached out to Arianna's mom, Ashley, via Facebook and told her. She can't recall exactly what she said but Ashley remembers her reaction.
"I was in tears reading her email to me," Booth, 27, of Pine City, Minn., tells KMSP. "It was pretty crazy. All I can do is cry every time I think about it."
Harding has also started a fundraising site
so Ashley's whole family can go to Disney after she recovers from the surgery.
"I just wanna say I just found out today that Christy wanted to do this for our family," Ashley wrote on the site three days ago. "I just cried (that happens a lot lol). I mean she's already saving my daughter's life."
Harding still has no idea what made her go to Arianna's Facebook page that day.
"I can only think it had to be an angel whispering in my ear because I never stop on those," Harding tells PEOPLE. "It's too emotional. But I did. I think it's just one of those things that was perfect timing."
She says she's a little nervous about the surgery but is more concerned about Arianna.
"People say this is something that is harder on the donor than the recipient but I don't think that could possibly be true," Harding tells PEOPLE.
"This is not a cure," she says. "This is just a treatment. This is something she will have to live with forever."
So she had one request for everyone.
"Keep up the prayers," she says. "There's still so many things that can happen."