The woman, who would have turned 76 next week, died after being treated at a local hospital for a brain bleed and severe burns, police said.
Katleen Chafin was told by her priest that "giving birth out of wedlock was equal to murder," according to her lawsuit.
President Donald Trump claimed LGBTQ Americans are among his "biggest supporters."
The two men from Florida and Virginia went fishing Friday on a 24-foot boat. Their disappearance has sparked a massive search.
The rally, scheduled for Sept. 14, will be held just five minutes from where the shell of the former nightclub still stands.