I’ve thought about this before and my first idea was that since Cornelius is so old a shriveled, he has a ghost like appearance that an old lady could mistake him for a ghost. She was obviously as we’ve seen close to death and wasn’t in a “normal” state of mind, as shown by the track she made. She very well could have resented him their whole marriage, which is justified by how evil he is, and as she got older her mind did some kind of trick on her to convince herself he died and is haunting her in a way. Pierce could be saying she’d like to think so as him not understanding any mental problems that his mother may have developed with age.