Is it normal for my 6yo daughter to go pee 8 times/day?

Maybe, maybe not. Frequent voiding urine is not necessarily abnormal, could even be a habit. There are a few warning signs and symptoms: feeling constantly thirsty; pain associated with voiding; cloudy smelly or red urine; new-onset bedwetting; weight loss; history of severe dehydration disproportional to the degree of diarrhea/vomiting.