'I want to save her life': Sister donates bone marrow to big sister battling leukemia

Big sister, Sarah, 17, was diagnosed with acute lymphoblastic leukemia.

Little sister, Savannah, 13, said hearing the news was "heartbreaking."

Sarah needed a bone marrow transplant, and Savannah was a perfect match.

"She's my sister, and I want to save her life," Savannah said.

Their mother, Sandy Thornton, said Sarah had always been a healthy teenager.

"It hit us like a rock. She had a sore throat, and the next thing you know, we're in the hospital for five weeks," Sandy Thornton said.

"I got really excited because if not, I would have to wait years to find a bone marrow donor," Sarah said.

Over the last three months, the family has traveled back and forth from Mount Olive to Chapel Hill.

Sarah has not been able to go back to school.

"God has a plan for everything ... I really think he's going to let me be a nurse," Sarah said.

"Sarah is my strength. When I get upset and I cry, she rubs my back and says, 'It's OK Momma. We're going to get through it. God's got a plan,'" Sandy Thornton said.

"She's my best friend," Savannah said.