"She is cooking a German meal."
Translation:Elle cuisine un repas allemand.
Cuire is a bit different. An oven or a stove can "cuit" something, but unless you have heating elements in your hands, you would say "fais cuire" (have or cause it to be cooked) with this verb. Cuire means the subject itself is acting as the heating/cooking agent. You can also describe something as "cooked" using cuit. le saumon cuit/the cooked salmon, du riz cuit/cooked rice
"Cuisine" is also a verb "cuisiner" and it means "to cook." Elle cuisine un repas allemand is correct.
Most of the time the adjective follows the noun, but there are certain adjectives that precede the noun. You can find more information in the Tips & Notes here: https://www.duolingo.com/skill/fr/Adjectives-1/tips-and-notes
Why is nationality adjective capitalized for German meals but not capitalized for American Sandwiches
Usually the program allows for one typo or mixed-up letter. However, Duolingo isn't a human teacher that can detect a simple spelling mistake from an entirely incorrect word. On the other hand, it is probably best to be aware of any spelling mistakes so that you can fix it for the next time, rather than repeat the same error over and over until is memorized incorrectly.