A guess about the ending of Messud's The Woman Upstairs

I have a thought about Claire Messud's The Woman Upstairs, and if you haven't read or finished it yet this may be a spoiler - or I may be completely wrong. Wonder why I didn't see this sooner. It's possible that the narrator, Nora, the eponymous woman upstairs, is actually the "madwoman in the attic," that feminine trope, maybe the descendant of Gilman's Yellow Wallpaper protagonist. That is, I've been sensing all through the first third of this novel that there's something incredibly off about her relationship with Reza (her 3rd-grade student) and in particular with his mom - they share an art studio and Nora is attracted to her in ways she can't comprehend or explain - and his dad, who has been coming on heavily to Nora and who shows up unexpectedly in the studio and makes tea and generally behaves inappropriately - far too forward and flirtatious. Nora is attracted to him, too - to the whole family - and is deeply hurt that they don't contact her over xmas vacation (they return to Paris for a visit; this after their son injured in a bullying incident) though they welcome her openly on their return. So: my sense is that either they aren't real at all or, if they are, the entire relationship between Nora and the two parents may be her fantasy or delusion. Do other characters ever see them together (a la Sixth Sense, that great movie)? These characters seem to be filling some kind of psychological void for Nora, and they don't behave in a totally normal way, either - if I'm wrong in my guess, this may be a flaw in the novel or maybe it's a cultural gulf (they are "foreign" academic visitors to Cambridge) that Messud is examining. But I think I'm right - these characters will prove to be illusions, or delusions, and Nora will spin deeper into her troubles - we don't know from what later vantage she is narrating this tale, but it could be from a hospital or perhaps a prison (the story does seem to be moving toward her taking some drastic action re Reza, such as abducting him, presumably for his own well-being). Messud's reference to Chekhov's The Black Monk, about a man suffering from delusions, is another hint; and her obsession with tiny constructions of women imprisoned in room, oppressed and depressed (Dickinson, Woolf) is no doubt another dark foreshadowing.