Honestly, kids are brutally honest like that! My little cousin said the same thing about my pancakes once. You gotta load those cookies up with extra chips, maybe even some mini M&Ms for color. It turns a "sad" cookie into a party cookie real quick.
Hold up, she's eight and already a food critic? That's brutal. Your cookies just got a one-star review from a third grader. Better double the chocolate chips next time.
Kids have weird taste buds though. My nephew will eat a whole bag of sour gummy worms but calls broccoli "spicy." Maybe the cookie texture was off, not the flavor. A little underbaked and gooey can feel wrong to them. It's not always about more sugar.