Yes, girl is a Scrabble word!
...and is worth 5 points in Scrabble, and 7 points in Words with Friends
girl
Noun
1. A young woman
2. A youthful female person
3. A female human offspring
4. A girl or young woman with whom a man is romantically involved
5. A friendly informal reference to a grown woman
What Scrabble words can I make with the letters in girl?
3 Letter Words
2 Letter Words