As long as she wrote it as a private person, to a public press (this might be different if it had been printed in the university paper, where it could have been seen as an official statement) then she is free to say that if she chooses. Fact of the matter, I've always been been a bit leery of that comparison myself and I never use it.
She is going to get a huge check, at the expense of the taxpayers of Ohio, and then get a nice job with some Christian School.
As long as all she did was express her opinion, and took no action in her job to prevent it, she is within her rights, even if you don't agree with her.
There is a deal going on here (California, but not SF) about the clerks giving out marriage stuff to gay couples, and the deal is... "you don't have to like it, but you do have to do it."