She didn't try to "worm out" of anything. The question was badgering. She wrote an entire book laying out her thesis and rather than discuss the contents of the book, Matthews wanted her to accuse an individual of treason so liberals would have one sound bite they could use over and over again.
If you write a book where the thesis accuses the entire Democratic Party, past and present, of treason, then you should be prepared to be questioned on individual names. How is that "badgering" for Matthews' to ask her about JFK? And Horowitz showed just how ignorant she was in that response.