All she has to do is show up. The dems and anti-Trumpers will declare she is credible no matter what. The reason, I think, she is avoiding anything in a formal legal declaration is her fear of what Kavanaugh will do if she sinks his nomination: He will sue her and she will lose everything: he will get a judgment so high even Soros will not cover... this will include any future profits for appearances, book deals etc.
Please, someone inform me that he cannot do this.