The sentence with the modifying phrase placed incorrectly is:
"Ana wants to buy new athletic shoes from her favorite store once she saves up enough money, Shoe Empire."
The phrase "Shoe Empire" is incorrectly placed; it suggests that "once she saves up enough money" modifies "Shoe Empire" instead of "Ana wants to buy new athletic shoes." A clearer and more correct rephrasing would be, "Ana wants to buy new athletic shoes from her favorite store, Shoe Empire, once she saves up enough money."