Hi there and welcome to Just answer!! I am Dr. Loretta, a licensed veterinarian and I am happy to answer your question.
Cocoa rolls in things as an instinctive trait ....in the wild, this will hide their scent from predators so they always feel like they have to do this...
She is just being grumpy or spoiled if she growls if you don't scratch her...this is a very sensitive spot that most dogs like having scratched. I am sure she means nothing by it but if she continues to do this, discourage this "aggressive" behavior by saying NO! It is best to nip this type of behavior in the bud.
Good Luck! Sincerely, XXXXX XXXXX