My 12 year old takes hours to get to sleep

My 12 1/2 year old daughter takes on average three hours, from turning her lights off to falling asleep. She is also very restless, and when I have had to sleep in the same room as her (hotels etc) I have found she is turning over and moving alot more than what I'd call average. When she was younger, she didnt have a proper nights sleep until she was 4, and she never took a nap in the afternoon, even though I encouraged her greatly. Why? Is there a reason for her taking to long to drift off? She doesnt get up from her bed at all, and she wakes in the morning at the usual time... Usually she gets into bed with the lights off at 10, maybe 10:30, and wakes at 7:30 school days, 10:00 weekends. Thank you. (She doesnt act tired during the day, and no matter what time she goes to bed she will take 2-4 hours getting to sleep)