What are symptoms of dyslexia in a 6 year old girl?

Comprehension. Difficulty in reading comprehension is the major symptom. There are several different types including "seeing" the letters backwards.
Inability to sound . out or decode words is a sign of reading disorder. A 6- year-old should be able to tell you how many sounds are in the word "cat". Some dyslexia is from a visual-perceptual problem. Mostly it's from inability to process phonemes, the smallest units of sound in a language. Ask her teacher if she is having trouble with sound-symbol association, or what sounds letters make.