I have seen that a doe will adopt fawns that have lost their mother. Either due to hunting, car kills or just simply lost her out in the woods. But another thing is that, whitetails are very social creatures and will most always hang out with others except probably during the rut. The whole safety in numbers thing. At 7 1/2, I can't really think that she has too many more years at giving you offspring. You might want to think about taking her in the next season. Unless you and your hunting party thinks that she deserves to be taken out naturally. I couldn't imagine trying to eat with the worn down teeth she's probably got. With that in mind...you might be saving her from starvation by taking her. Might not be good steaks though. You always hear of hunting groups that make a certain animal "off limits" because of some certain thing that happened, but there has to come a time that they will go. Do you want it to be a hunter(that makes an ethical kill) or a car or coyote/wolf?