She was not right about her son, and I think she was a sellout and loved the spotlight. Sellout because she sold items of her son, pictures, letters (some with an audio recording of her reading it), clothes, other personal items. She wouldn't stick to the same story either, she even in 1966 said this; “Now, maybe Lee Harvey Oswald was the assassin. But does that make him a louse? ... As we all know, President Kennedy was a dying man. So, it is possible that my son was chosen to shoot him in a mercy killing for the security of the country. And if this is true, it was a fine thing to do, and my son is a hero.” - Marguerite Oswald A mother in history - 1966 Then she turned around in 1967 and said Billy Lovelady on the porch was Lee Harvey Oswald. Why? Because it was a way to stay relevant in the cameras. I don't think for a second she actually believed her son was innocent. She was definitely hurt by his death, but she tried to exploit his death for fame and money.
Haha! That tired old theory is still around huh? Why not blame Jackie or Connally while you're at it! Maybe JFK brought his own pistol and decided: "Screw it! I'm done heah!" ;-)