She's level 10 in the cooking skill. Is there a certain way you make it, I thought all you had to do was click the fridge.
Try having your sim watch the cooking channel for awhile and see if she can learn a pet recipe.
I had the same problem with one of my sims. Jeff is level 10 cooking but is from a game before pets that I move into Appaloosa Plains and he didn't have the option to make pet food.
Yesterday he was watching the cooking channel with his new wife ,Mollie, and he learned the recipe for chicken pet food. Now he has the option to make gourmet pet food but the only option is chicken pet food.
On the other hand, Mollie who just made level 1 cooking has the option to make gourmet pet food and she can make chicken, duck, beef and fish pet food and horse granola.
I've checked the bookstore and library for recipe books for Jeff but haven't found any. So I guess I'll have Jeff watching the cooking channel and see if he can learn the rest of the recipes.