I'm pretty sure her mother is
I think Scarlett has a confused identity though. Children of the intermarried are probably raised with no religion or some of both. She probably doesn't consider it to be important to her--maybe they lit a menorah for Chanukah when her and her mom were living with her grandmother and maybe she celebrated Christmas when getting together with any of her father's relatives.
Scarlett Johansson doesn't believe in monogamy, but claims to not be promiscuous when in a relationship. She shouldn't be having so much pre-marital sex anyway. Apparently, she gets tested for HIV twice a year. Maybe that's supposed to be a reflection of her past relationships--that she'd have some doubts whether her partner was being monogamous and whether he had any sexually transmitted diseases.