No kidding, your daughter is too young to have stinky feet. If she were a teenage boy, it wouldn't be too uncommon but she is too young to have that problem. One of my son's had stinky feet at a young age. I tried washing the sneakers, baking soda, etc. on his feet. He had a fungus infection commonly called athlete's foot. He didn't have any other symptoms such as cracks between the toes or itching either. Within a day of using athlete's foot medicine, the odor was gone. He continued using it for 2 weeks and has been completely odor free for over a year. Now whenever anyone's feet in my family start to stink, we buy over-the-counter athlete's foot medicine , treat the feet with the medicine, and then wash all the shoes and the problem is solved.
It's very hard to distinguish a bacterial infection from a yeast or fungi infection so you might want to take her to the doctor first.
Bev