You might have to make some alternate plans so you can attend preference that one time -- hopefully it will be held in the evening. Once you're in a sorority though it shouldn't ever be a problem. In my experience religious obligations are
always respected.
I'm certain that all NPC sororities have non-discrimination policies regarding religious beliefs. No one is going to think less of you and it's not going to lessen your chances of getting into a sorority. Not to worry.
