What if she just responded to “I AM ALL THE SITH!” with “I am a Jedi.” She’s finally accepting her role and place in the story, and it’s a nice callback to the “I am a Jedi, like my father…” from ROTJ
Actually, changing this line would also bring more symbolism about the opposition between Sith and Jedi (although I don’t know so much about the SW lore) : the Sith get more and more powerful by having the master taking control of its apprentice (as explained in the movie, thus why Palpatine is “all” the Sith), while the Jedi become more and more powerful by passing on their knowledge to the new ones (thus saying that you’re “a” jedi is enough to imply that you carry with you all the Jedi knowledge, an idea pretty well symbolized with the Force ghosts in the scene).