A McDonald's hamburger is not the best thing to feed a dog - even as a treat. It won't kill her, but depending on her size, the salt, the bun, the ketchup, mustard and especially the onions will upset her digestion, possibly causing uncomfortable gas and diarrhea.
Can my dog eat a cheeseburger?
Chances are, your burger has added salt and spices and topping that can be dangerous to dogs, such as onion. However, if you want to through a plain patty on the grill, hamburger meat that is unseasoned and cooked can be a healthy source of protein in addition to your dog's regular balanced diet.
Can dogs eat at McDonalds?
Now, What is OK For my Dog to Eat at McDonalds? As long as you keep them as basic as possible and feed them in little portions, most of the food from McD's is fine for your dog to consume. However, remember this: For every pound your dog weighs, you should only feed 25-30 calories.