It's my opinion, that if they can't make it without her at this point....they aren't going to at all. They are old enough, know the area good enough(for escape routes, water holes and food) and have been eating solids for long enough to be able to survive without the doe around. I even saw the other day that a fawn tried to nurse and mom kicked her square in the side. Pretty much tells me that she is trying to cut her off or already has. Not to mention that deer are very social animals. The fawns will hook up with other doe if they haven't been running in bigger doe/fawn groups already. It's not like are going to be spendy long cold nights by themselves.