Unless she has converted, she is a gentile. Islam is passed down patrilineally (such as The Messiah who had a Muslim father), but Judaism is determined by the mother, matrilineally.
It was out of curiosity, I looked up Gwyneth's parents in Wikipedia. It is the matrilineal descent that determines the religion in Judaism.
I had always wondered if Islam was a faith of law being born into like Judaism, or if Muslims were born Arabs and converted to being Muslim....