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 ambiguously placed at the end of the sentence, making it unclear if it refers to the store or something else. A clearer way to write this would be: "Ana wants to buy new athletic shoes from her favorite store, Shoe Empire, once she saves up enough money."