Meagher was smart and literate but she revealed, to her credit, her mindset, her motivated reasoning if you will, when she said that when she heard that JFK was shot her first reaction was, "They are going to blame a communist for this." Her first thought. It was not, "Is he dead? Did they catch the people?" but "they are going to blame a communist."
This was something that affected all of her analysis of the assassination. She really did see Oswald as an American Alfred Dreyfus but instead of anti-semitism being the cause for the frame up she saw anti-communism as the reason for "Oswald-as-patsy". It was the anti- anti-communism view of the Left that saw opposition to the Soviet Union and communism as a greater danger - McCarthy and the Red Scare - than Moscow. As Fred pointed out, she was very critical of Garrison, again to her credit, but when he later said that Oswald was innocent she came to if not defend him at least no longer wanting to exile him from the assassination community. And if I have it right, she never really did give an explanation as to what happened, who did kill JFK. She was focused on exonerating Oswald and not saying what happened (which frankly, is a cop-out).
In order to defend Oswald in both the murder of JFK and Tippit (which she also did) you really have to have a deep conspiratorial worldview. She was closer to thinking like Garrison then she realized. I think Tom Bethell said when he met her at her house that it was filled with UFO books. He said to himself, "Oh boy, here we go."