So something that's bugged me before about the book has popped up in my mind again. We first meet Anathema when she's 8 years old, when we are told that her mother 'happened to read the word one day and thought it was a lovely name for a girl'. Wouldn't she already know that her daughter has to be called that? I mean, she's in a prophecy by name, and her mother would know that the timing is spot on for her to be the same Anathema referred to by Agnes, as apparently the date of the apocalypse is known to be 11 years away by the time Anathema is 8 ('She was too young, and too self-centred at this point to attach any importance to the fact that there was no mention made of her children, or indeed, any events in her future further away than eleven years' time').
I suspect that the only reason is sloppy editing.