We live in the south and have long hot summers

.My youngest had the same problem with his feet

. Summer sandals and tennis shoes were terrible after he wore them for a bit

. I found out that if I kept his feet/shoes from getting wet they smelled fine. Don't let her wear her sandals or shoes for water play - buy some water shoes -
Walmart has them for around $4 for yard/water play

- and keep her toesies dry with some of the above suggestions and she should be fine.
I found that even if I dry the shoes once they have gotten wet, they are done for as far as smell and his poor little feet would stink to high heaven

. I'll have to try the freezer solution. You have to be sure that her feet are dry- you can blow dry her feet but they must be dry

before you put her slippers on or shoes/socks or any covering. Let her run around the house

bare footed to allow her feet to "breath" and dry out- it will cut down on the bacteria that make the smell.
HTH
