Who is the Rascal Flatts song "Skin" about?

The story of a girl from Kentucky named Sarabeth who falls ill, and while ill, she notices a bruise that won't go away. After being taken to a hospital, she is informed that she has leukemia ("between the red cells and white, something's not right") a form of cancer and must go under chemotherapy. She is afraid of the effects it may have on her (most notably, hair loss), and holds onto the dream of dancing with her boyfriend at her high school prom.

When she wakes the morning before the dance, she notices that she is virtually hairless, and cries while being embraced by her mother. Sarabeth thinks it would be a mistake for her boyfriend to take her to the prom in this condition.

Close to the prom, her boyfriend arrives, wearing a baseball cap. When he removes it, all are emotionally surprised to see that he shaved his head to show sympathy, and is willing to accompany Sarabeth to the dance. She realizes her dream has come true when they go to prom and they dance. As the song says, "Her very first true love is holding her close... And for a moment, she isn't scared."