Several years ago I hunted an area where there was such a doe. I called her Grandma. She busted me every day for 3 days straight in 3 different stands. and it was like you said. All the deer with her were relaxed and care free but she was always on alert, head up and nose into the wind. She was old and gray in the face but her senses were keen. My guess is she probably died of old age.