I was working with a young pitcher today and your DD and her sound similar. The young girl I was working with today was turning her landing foot past 90 degrees (heel was further forward than toe) and landing with it over the power line. She would try and compensate by bending toward third and swinging her arm around the plant foot. I was trying to have her focus on getting the front foot to point forward toward the catcher, 45 degrees, and land straight down the power line instead of on the third base side of the power line. It's hard to work with groups when there's only limited time.