She had agreed, but she was finding it harder than she anticipated, what with Preston’s snooty attitude.
Ok, so without the evidence he presented, I'd say he was being snooty, too— but it has been established that Preston is a character who is most concerned with finding the truth, and he has compelling evidence that the theory he is investigating is not unfounded.
Effy just can't separate herself from Angharad, step back, and view the situation from a healthy distance. She has made the book such an integral part of her identity that its sacredness will not allow her to accept someone else might have written it.
