If one doesn't actually mean it when she said "til death do we part," did she actually get married? The vow's legitimacy is essential to the marriage's validity.

That's right. It's not legit to see marriage as a romantic contract agreement with exception clauses. Deep down, that's not what men and women really want.

No, it really isn't. Wanting commitment means it also being required, which can hardly be done if the state will issue a clean slate and half your income if she crys in court, and not even convincingly. Someone should author a prenuptial agreement template that binds the two to the old, permanent version of marriage and prevents no-fault from even being an option.