Prayers for her sweet soul and for her greiving family.
I don’t think she was a Muslim, although the boyfriend she went to Syria and was captured with probably was (he was released, btw). So I think “God” didn’t necessarily refer to Christianity but at least to the Judeo-Christian concept of a loving God, which is held even by a lot of deists, such as Unitarians.
Prayers for this poor girl. I hope she died in the attack and was not put to a horrible death.