You answered your own question. They need to obtain the legal exemption on their own without any help from you, or they are excluded per state law. I'd give them the list of outstanding vaccinations and resources to obtain said vaccines, with a "by this date".
I'd say to the parent, "as a nurse, I can give you information on vaccines, mandated schedules and resources to obtain the needed vaccines for school. If your religion forbids vaccines, your minister or church officials should be able to walk you through the process."
If this is truly a religious thing, she should know the drill.