Why is my 14 year old sister suddenly showing signs of dyslexia?

She's always been a straight A student. She's been reading since age 3 and she's been in the gifted program since kindergarten. She's never had any head trauma or any really traumatic experiences. I mean, come on. This girl read Harry potter 1-3 in 1st grade and Gone With the Wind in 7th grade. Now, she is having trouble reading. Why?