Sleepy Rosie, you asked what would happen if a witch wanted to say a prayer for a catholic. I already posted an answer to that but the post was deleted so I must have said something wrong. I'll pare the answer down this time and hopefully you'll see it. This would be my response anyway, others will have to answer for themselves -

In short, I would just tell her politely 'no, but thanks anyway' and leave it at that on the assumption that he / she meant well. I would only get shirty if he / she persisted after I'd made myself clear (not once, but twice or thrice) in that manner. I wouldn't 'report' on him/ her (though if I understood correctly the old lady didn't 'report' on the woman, but mentioned it as a curiosity to whoever else was helping her)