What breeds of cat have double coats?

she's probably a tortoise shell mixed with an american shorthair. Both cats have thicker furs and the american shorthair is pretty husky and fat. I have an american shorthair tabby and he fits your description too. of course she might be maine coon like you suggested since maine coons need very thick fur since they were born to live in very cold climates. so probably maine coon tortoise shell. :)