Everyone has their own preference when it comes to harvesting a doe. Some like quantity and shoot large does, some like quality and shoot young does, some will not hesitate and harvest a fawn for their freezer (they do taste good!).
To me, the best doe to shoot, is the first one that gives me the opportunity, regardless of size. However, I do try to avoid shooting fawns to prevent the harvest of a buck fawn.
Good luck and be safe