"Essentially [we were] living in a hospital for four weeks straight," she said.
Looking back, she laughs. "I think we broke some hospital rules," she said, remembering a nurse who was angry about them staying overnight.
"We'd just say, 'If you had a 2 year old with leukemia, you'd stay here too,'" Renee said.
For eight months, the family watched as Isabella's head of hair turned scraggly and fell out.
For eight months, the family drove back and forth from its home in State College to Hershey Medical Center.
For eight months, the family fought to defy leukemia.
On Nov. 1, 2003, they won. Doctors told the family that Isabella was in complete remission.
Isabella doesn't remember the battle, but her parents will never forget it.
But neither Isabella nor her parents will forget Thon.
"It's just a really special weekend for us as a family to have time together. It's great to see the nurses, doctors and the other families. That's probably the most special part -- getting to see the other families," Renee said.
This year will be the family's fourth Thon. Renee is looking forward to seeing other Four Diamond families because "they're the only people who really know how you feel," she said.
Isabella remembers getting her face painted and getting a manicure at last year's Thon. Acting bashful, she expressed face painting by rubbing her face and manicure by pretending to color her fingernails with crayons.
Isabella was excited about staying up for the pep rally last year, Renee said. The Student-Athlete Advisory Board, which sponsors her, usually hosts its pep rally around midnight -- well past Isabella's bedtime.
Memories of Thon and check ups every three months are a few reminders of the struggle for Isabella, which usually seems far from her mind. Now she spends her time in kindergarten and playing with her 18-month-old brother, Jack.
AML is not hereditary, so Jack does not get tested.
Renee, a Penn State alumna and kinesiology instructor, remembers when she was a student and Thon was held in the White Building and then moved to Rec Hall. She's looking forward to Thon in the Bryce Jordan Center this year.
"I'm really anxious for it to be in the Bryce Jordan Center. I think there's a lot of potential for growth," she said. "It's changing with each move, and it's only gotten bigger and better."
Leukemia survivor and Four Diamonds child Isabella Messina, 5, lovingly touches her mother, Renee, in their State College home.