Born with hypoplastic left heart syndrome and double outlet right ventricle, Athena spent her life in the hospital, Willard said.
She said Athena lived with the aid of an extracorproeal membrane oxygenation machine.
"She was on that machine longer than most people are allowed to be," Willard said. "Some people on this (machine) bleed in their brain or their stomach, but she had no side effects."
Last month, Athena's family hosted a car wash to raise money for a heart transplant that would hopefully allow the girl to survive. Athena never received that transplant, Willard said.
As they waited for a heart, Willard said she told her daughter every day to let her know if she needed to stop fighting.
"I told her to let me know when she could not fight anymore," Willard said. "She squeezed my finger every day for a week, even though she did not like the feel of the glove (that reached into her care unit). On Friday and Saturday, she did not squeeze my finger. That was her sign that she was ready to move on."
Most of Athena's family went to the hospital to say goodbye Thursday. Willard said the girl was christened that day.
As she sat in her car Friday waiting to talk to a funeral home about arrangements for her child, Willard said losing Athena did not come as a huge shock.
"I am doing better than expected, but that is because I really took to heart what she taught me," Willard said.
Athena's short but full life was a lesson that all life is a gift and that not a single moment of that gift should be taken for granted, Willard said.
"She did not just die, to me," Willard said. "She moved on. When my time comes, I know I will see her again. I got to hold her to her last breath. Even then, she gave me such a sense of calm and peace."
A previously scheduled fundraiser to benefit Athena was held Friday at the New Delmar Inn Lounge west of Hagerstown.
Owner Henry Nigh said there was a DJ and $5 was collected from each person. About 25 people were there as of 8:45 p.m., he said.
Staff writer Andrew Schotz contributed to this story.