This thin old doe was all alone and grazing. She's very skinny, but there's plenty to eat so my guess is that she's lost teeth, has cancer, or is being eaten alive by parasites.
Deer get to age 7 or 8, if they are lucky, and that's about all they wrote. For animals in old age, the best they can hope for is a swift death from a hunters bullet. She will make it through the summer, but if she does not ad weight, I doubt she will make it though another winter.