Who is that girl Mandy who is the girl in the song Mandy by the Jonas Brothers?

Mandy is a childhood friend of the Jonas Brothers. She was also a student of Denise Jonas, who taught her sign language. Denise was the one who introduced Mandy to her sons. Later on, she went out with Joe, but then decided that they should just stay friends. So, she is also Joe's ex. Even though they broke up, Mandy and all of the Jonas Brothers still remain close friends.