The sentence with the incorrectly placed modifying phrase is:
"Ana wants to buy new athletic shoes from her favorite store once she saves up enough money, Shoe Empire."
The phrase "Shoe Empire," which is intended to clarify the favorite store, is incorrectly placed at the end of the sentence and makes it awkward. It would be clearer to rephrase it for better clarity, such as: "Once she saves up enough money, Ana wants to buy new athletic shoes from her favorite store, Shoe Empire."