“Heir to” sounds preferable to me, more formal than “heir of” in the way I feel these title crawls should be.
The Jedi in this sentence is or are the total package. Rey is heir to all that the Jedi were and had. “To” communicates that she inherits their sum totality, whereas “of” sounds like the Jedi are passing something down while remaining distinct. Like maybe they left her their beach house. I think that book title gets it right.
“I’m the best kind of correct: technically correct.”