OK, first let me say that even though Serena is not my favourite player, I am really upset for her and for tennis that she can't play. There are others catching up, but if she played she would be the fave to win, no doubt about it.
BUT, part of being a professional is about keeping yourself well, fit and uninjured enough to play. Hence, if Serena was not able to manage a full year uninjured , then whoever wins in her stead completely and utterly deserves the win because they were able to get themselves there in one piece to play. Of course it gets complicated where the injury has nothing to do with the way the player has chosen to handle her career (eg Monica's tragedy) but nevertheless a tournament is held between the 128 people who are able to play, and thus the best of those deserves the win.