Jehovahs Witnesses are not treated like scum. And your mum has a case for unfair dismissal based on religious discrimination. I am sure DiamondBlues PM will point you in the right direction.
When I was a Witness I found for 30 years that people generally, though puzzled and sometimes repulsed by my beliefs, never treat me like scum. At worst they just couldnt understand, for instance, the blood issue. And now that I am not a Witness I can see how puzzled they must have been and in general how very restrained they were in their treatment of me.
Good luck to your mum. She may well be better off not working with people who feel free to flout the discrimination laws of our country.