Simply put, Elly has a problem she doesn't seem to be aware of and denies having when it's pointed out to her because she unfailingly focuses on the downside of every blasted thing that happens to be and magnifies how bad bad is going to get. Casually being told she's an alternate means that no one actually wants her to speak. Lizzie's developing a distinct personality and starting to stand up for herself is a horrible tragedy in which her innocent baby has been replaced by a monster who wants to beat her poor mother to her knees because that's the same thing that happened to Michael. April's arrival isn't a blessed event but actually THE WORST THING EVER because she's stuck with diaper rash instead of a career and her dreams of travel and a career were derailed forever......until they weren't.
This sort of thing makes me wonder if just maybe, Elly is a tragic character with a fatal flaw: a biological inability to be satisfied for very long because of an exaggerated fear she doesn't realize she has that if she relaxes, people are going to appear from nowhere and rip her into mincemeat just for shits and giggles. She is capable of enjoying things for oh-so-brief moments of time but sooner or later, the voice in her head that fears attack dominates the internal conversation and there she is again, turning a free lunch into a cruel imposition by monsters who seek her downfall. She only occasionally admits to the demon of terror and hate that holds her and her family hostage but most of the time, she denies its existence because admitting to it makes her not normal.