In the O.P.’s case, however, there might be nafka minas. Is her friend’s budget such that getting these items for free would cause her to buy something else that she would not have bought? Is business such that the items would have been sold anyway?
In any case, if it is an issue of gezel it does not matter who owns the store. Even if it is something else that only applies to Jews (absent chillul Hashem) I see no reason why it should matter if the owner is frum. It is not, for example, allowed to charge a non-frum Jew interest on a loan.