The best way to rewrite this sentence to avoid duplication is "Selena was surprised when she attempted to duplicate a copy of a dish she learned in culinary school."
A surprise by definition is unexpected, so it's a bit redundant to say an unexpected surprise. Also, saying culinary twice isn't necessary. It is better to just use it to describe the school and from there it can be inferred that the dish is culinary.
Answer:
Selena was surprised when she attempted to duplicate a copy of a dish she learned in culinary school."
Explanation:
