In "Food for the Common Cold," what are David's mother's and David's grandmother's opposing opinions about telling Frick about the hysterectomy?

David's mother is trying to convince herself that a miracle could allow her to have more children, despite the fact that she has had a hysterectomy. But she is not really wishing for more children--she is really just wishing that she did not have to tell Frick that it is completely impossible. She does not want to try to have more children, because she is frightened that she might have another pregnancy like the one that resulted in Frick's malformed twin.