The theme of extortion revolving around an aged and recluse Golden Age of Hollywood movie star was first done in The Illusion of the Stainless Steel Lady (1974).
Gloria is reading a section of a newspaper in her bed. On the back page, there is an advertisement for a CBS sitcom ("Busting Loose"). Charlie's Angels aired on a competitor TV network, ABC.
Kelly suspects that someone is trying to do a "gaslight number" on Gloria Gibson. "Gaslighting" is a term used to define a form of psychological warfare designed to drives its victims to doubt and question their perceptions of reality, often dismissing their claims as figments of the imagination. The term is taken from the title of the 1938 British play, "Gas Light," which play was later made into the George Cukor film Gaslight (1944). Given the phrasing and the year, it's likely Kelly was more directly referencing the movie than the psychological term.