There are a lot of good points supporting a pretty good thesis. However, I would argue that every relationship that produces interdependence needs a system of management and external arbiters when there is disagreement over the terms of dissolution. That doesn't need to be the state, but I don't know what could replace the state's power to enforce equitable dissolution in the face of acrimonious separation.
I question her claim that divorce requires the permission of the state. Yes, not everywhere has a true no-fault rubber stamp comparable to the rubber stamp of most civil unions, but I think that is the trend. These days, at least in Canada, the biggest role of the state is in enforcing the negotiated terms of dissolution and in protecting the interests of any children. The state also is forced to intervene when there are egregious failures to negotiate terms.
The state and corporations could completely ignore marriage as a foundation for anything at all and we'd still need a way to prevent damaging, destructive, and sometimes deadly outcomes from the breakdown of relationships.
I view marriage in much the same way I view any other contract. There are formal, written contracts and common-law contracts. Both have to be entered into freely. They have to be mutually beneficial. The contract terms need to be negotiable over time. The dissolution must be accounted for or at least handled without unduly compromising either party's status in the community or their prospects for the future.
My wife and I are sneaking up on our 50th anniversary. We didn't see the point to formalising our marriage 50 years ago with trip to the courthouse, but, at the time, that was the easiest path socially, financially, and legally. And let me tell you that going the courthouse route was vilified in certain circles even more than our "shacking up" had been. It was seen as a way to cheat the system.
Our anniversaries are evaluations of our relationship, our prospects for the future, and private celebrations of our individual growth and of our growth as a couple. Someone threw us a party on our 25th and I'm guessing that will happen on our 50th. We choose to recognize that as our friends and families joining us in those acknowledgements, even if that is not the language they use.
There have been several times over the years when those evaluations were the foundation for what can only be called renegotiations. If we had been truly invested in the formal institution of marriage, we would have had recommitment ceremonies of some kind. We actually discussed doing so, but neither of us thought our marriage certificate was worth the paper it was written on. Instead, all of the value in our relationship is in the relationship itself and in our personal, ongoing commitments to ourselves, to each other, and to the relationship.
In the end, I'm "anarchist-lite". But I'm also "libertarian-lite", "socialist-lite" and a bunch of other "there are good points and great ideas, but let's not get too extreme" points of view.