Erroneous! Erroneous on all counts!
As much fun as conjecture can be (hence the vast web of fanfiction based on many a cult classic) I think this thread is innappropriate for this particular novel.
I've read war and peace in its entirety several times and I frequently return to bits and pieces of it when I am between books or merely nostalgic. One of the most important themes in W&P is that there is no point in trying to divine the path a person may have followed had they made a difdferent choice. On the contrary, Tolstoy reiterates the inevitability of all that has happened and the utter irrelevence of contemplating "what-ifs"
Furthermore, it is natural for every character to behave as they do. There are no inconsistencies in any character in War and Peace, I suspect resulting from a deep understanding of human nature on the part of Tolstoy as well as much observation of men and women in his society.
Thus I don't think this question is worth discussing.
Also, the idea that Tolstoy intended that Sonya's life was wasted because she was not married is categorically untrue. He does clearly emphasize the sanctity of family love, but his definition of family includes not merely traditional nuclear families, but the "family" created by the web of love and loyalty developed through all the characters' respective relationships. (ie the lack of familial feeling demonstrative in the Kuragins' blood and marital relationships versus the fraternal love between the unrelated parties, Pierre and Prince Andre) To say that "Tolstoy clearly believed she chose the wrong path" is simply not well supported.