Firefighters and police were called to the house, in the Pasco County area of Florida, at around 1.45am after the girl's mother and nine-year-old brother escaped the flames.
At that stage the young girl was nowhere to be seen but she was located a few hours later and taken into custody. She reportedly sent her mother a text message after the fire, which read, "Mom, I'm so sorry. I don't know why I did it. Did any of [you] get hurt?"
The teen apparently told police that she had been visiting websites associated with the fictional Slenderman online character. Slenderman often appears in web forums dedicated to horror stories.
In a separate and unrelated incident in June of this year, two young girls repeatedly stabbed their 12-year-old classmate after they had become obsessed with the same Slenderman character.