Gymnastics is very complicated both physically and mentally. The number of correct repetitions of a skill needed before you REALLY have it (in muscle memory) are huge. I don't know your little daughter but have had three children who were/are high level athletes (including one level 10 gymnast and two AAA hockey players) and do know that this type of thing takes a lot of time. I agree with a couple of the other posters that you need to make sure that she really understands and feels what will be different if she has her feet together before she will begin to improve. After that, it will take a LOT of repetitions before she is consistently able to make this change. Please be patient with her.
Best Wishes,
ZZMom
Best Wishes,
ZZMom