Answer:
The reason why the manual thought his mom was confused was that before the passage it said, “His mother regained consciousness, but seemed to have lost much of her memory. She confused Manuel with her husband, and occasionally with her father.” The reason why Manuel came up with this conclusion was that it said, “Manuel was certain that there was no such girl, especially not with such a weird name. He suspected that mother got confused again, mistaking round Mrs. Valdez for a pretty girl. “Sure, Mom,” so he didn’t think that there was a pretty girl.