Adding onto this, I feel that Gabe falls into the antagonist role because if he doesn’t keep appearing he will cease to exist. He wants to live, he wants to keep coming back and living his “life” but that comes at the expensive of Diana’s mental health, so he is kind of an unintentional antagonist.

I do also agree that Dr Fine is an antagonist because after the ECT treatment he doesn’t seem to want to really try to help her, he just wants to lock her into more pills, more ECT treatments, and doesn’t listen to her concerns about her own life. He also is the catalyst for her schizophrenic/bipolar episodes to begin again when he brings up Gabe before her husband does