Just because she showers nightly doesn't mean her feet are getting washed. As a massage therapist I have smelled some rather disgusting smelly feet. One client told me she had showered, but there was a watermelon seed stuck to the bottom of her foot. Which, when I asked about it, she told me she had stepped on it the day before. She then said her feet were in the shower with her so they must have been cleaned. What she had failed to do is actually wash her feet with soap and water. After I brought this to my client's awareness, she now actually washes her feet and they smell so much better than before. So, just because your daughter's feet are in the shower with her doesn't mean she is washing them with soap and water. Then wearing the same shoes everyday, especially without socks, compounds the problem. You could try using "odor eaters" in her shoes.