Possessiveness

I have a mixed-breed female dog, about a year old, who I’ve had since she was two months old. She’s the sweetest dog. Unfortunately, she’s always had one issue: she’s possessive over resources with other dogs, and sometimes even with me. At home I can even take a ham bone away from her, but if she finds a puddle and starts eating mud it's a different story. Most of the time I can move her away without any problem, but every now and then she growls very intensely — and honestly, it scares me a bit.

Do you have any advice?