Gretta was only 15 years old when she thought her life was being torn apart. “It started at summer soccer practices, I just couldn’t keep up with the girls,” Greta told Ellen Degeneres. “I woke up one morning with a really sore throat, so my mom took me to the doctor, thinking, oh, strep throat, worst case mono and the results came back with a leukemia diagnosis.” Gretta couldn’t believe it. What had she done to deserve this? Gretta’s only hope of survival was to receive a bone marrow transplant, an incredibly painful procedure that also required a perfect donor match. Unfortunately, no one in Gretta’s family was a match. Things looked grim for Gretta, until a man named Danny Daniels changed everything. Danny, an army veteran, happened to be in the system because he attempted to serve as a donor to his friend 10 years ago. When he heard about Gretta, he didn’t give a second thought to donating. “As soon as I found she was 15, how can you not give a young person a match?” Danny saved Gretta’s life 10 years ago. Gretta, now 25, is about to get married and she decided to do something very special to commemorate Danny on The Ellen Show. Want to know what she did? Watch the video below to find out!