That being said, it's not one hundred percent her fault that Elly is an idiot no matter how panicked Elly's "overly strong" will and "abusive, controlling nature" made her. Sure, the same woman who angrily refused to even consider letting Jim have a dog because she read in a magazine that pets were on the way out went sat on Elly while indulging Phil because that's what she thought she was supposed to but let's be honest here. We are dealing with a woman who'd be an angry nitwit who'll die feeling jilted because she missed everything owing to wasting her life whining about what she doesn't have if Marian had been the most permissive human being alive. We know that Elly can't be happy with herself and feels compelled to do things the hard way because she has no sense of humor. We also know that she can't accept responsibility for her actions so she needs a scapegoat.
This is somewhat unfortunate because it blinds her to something that Deanna is also not aware of. Just as Evil Mira clearly seems to think that Deanna is a smarter, more capable person than the huffy, childish git who enables Michael, the part of Marian's Liography that wasn't about being unfair to Elly, domineering to Jim or indulgent to Phil was predicated on her belief that Elly could somehow magically be more than some dolt who'd wreck her life marrying a nerdy dentist who needed her to wait tables because he too was stupid with his money. It would probably not do any good to explain to her that her mother's disappointment with her stemmed from the fact that she saw intellect, ambition and drive that simply were not there because that would be a bummer personal responsibility trip.