I have a strong hunch that her message is going to be taken quite seriously both in California and in the rest of the U.S., in that, once same-sex marriage is legalized, it is entirely conceivable that such man-made constructs as "civil unions" and "domestic partnerships" are going to lose their legal standing, such as it is, and I would not be all that unsympathetic to that turn of events.
I do believe that these arrangements are inferior to the dignity and legitimacy conferred by the designation of "marriage," and it is very likely, once marriage for same-sex couples is institutionalized in a given state and/or society as a whole, that civil unions and domestic partnerships will become void.
The following statement may increasingly gain traction among the populace and politicians: "Now that same sex couples can marry, there is no longer any excuse for the State of California to encourage non-marital cohabitation, by opposite sex couples or same sex couples. California should shut down the domestic partnership registries. Cohabitation is socially and privately inferior to marriage. The state should insist that couples either put up or shut up: get married or be single. No more half-way house of marriage-lite."
I urge you to read her article, located here.