The sense of humor of a little girl

Months ago, Madeline created a game; I would prompt her, "Can you say 'Mama'?" and she'd grin and say "Dada!" Eventually she did say Mama, but never when I asked "say mama." Anyway, a few weeks ago I was reading a book to her before bed. She was particularly chatty at the time and repeated the words in the book after I'd say them. On the last page, it shows a little boy cuddling on his mom's shoulder, and the word printed is "Mama." I turned to the last page and read it, and Madeline immediately called out "Daddy!" Yes, she is a silly girl...