Anna Marie Kool,13, and Kristen Hicks,12, of Oxford, N.C., first met when they were five years old. They were in dance class;  Kool was struggling with a particular move and Hicks came to her aid, helping her with the routine. As Hicks instructed her friend, she never imagined how integral this instantaneous friendship would be to her life, never dreamed that Kool would one day help save her life.

Kool's 13 birthday is Friday and her wish is to raise money for Hicks, who just underwent a heart transplant in December. She's asking for 1,000 people to donate $13 so that Hicks and her family can pay their medical bills after her expensive surgery. Hicks is on 14 different medications that she takes four times a day.

When Kimberly Summer Hicks found out about Kool's request, she was floored.

"After I stopped crying, I wasn't surprised that Anna wanted to do something. I was just so thankful and felt so blessed that we had friends like this in our lives to help us through this," Hicks said.

Hicks was diagnosed with cardiomyopothy in November, a condition that enlarges the heart muscle. She recalled her thoughts when she first found out.

"I knew it was bad … I'm just thinking, this is not good," Hicks said.

She was placed on the heart transplant list on Dec. 1, 2011, and just six days later found out that her new heart was ready. She was in home in time for Christmas, a holiday miracle. But even her good health and good spirits could not make her family overlook the massive debt they had incurred, despite their insurance provider covering some of the expenses. They sought out the Children Organ Transplant Association (COTA) to help raise funds. COTA told the family to set a fundraising goal of $50,000 and has a website set up for Hicks.

That's when Kool decided to do something. Each year she takes up a cause; in past years she raised money for the American Red Cross and tsunami survivors, and collected toys for children in need. This year, she decided that her cause would be her best friend.

"It's the best birthday gift I could ever have," Kool said. She said that her desire to give comes from her desire to be more like God. "Jesus never left the lame person laying there. I want to be as much like that as possible."

"It's just a blessing to have her as a best friend, we've been best friends for a while. I know she loves me and I love her," Hicks said.

So far, they have raised $9,603.26. After ABC-affiliate WTVD aired a story about the girls on Thursday, they raised $3,000 in one day. Rick Lofgren of COTA says that "he's confident that they'll get the $50,000."

Kool is trying for Valentine's Day to present the donation to her friend and, in return, Hicks said that her best friend can expect a pretty awesome birthday gift.

"I haven't decided yet but I'm planning on buying her something good- maybe a heart necklace," she said.

A heart for a heart.