It's not unusual for children to have strong foot odor.
Kids are active and often sweat all over their bodies.
Keep your child's feet as clean and dry as possible. When she's done playing and is safely indoors, take off her shoes and socks so her feet can air out and dry off. Leave her feet naked or have her put on clean, dry socks. Bathe her feet daily to remove any dirt or old skin. You may also have to wash her shoes, which can harbor odors, dirt, fungus, or bacteria that contribute to your child's stinky feet.