Of similarity and siblings.

Of course, the real reason that Elly and her mother couldn't help but clash is that for all intents and purposes, Elly is sort of an inferior copy of Marian. She has her mother's awkwardness, her need to prove herself to indifferent authority figures, her exaggerated dread of what they both call 'chaos' and what less depressive personalities call 'regular life' and the same stubborn pride. Elly simply lacks her mother's keen intellect and firmness of character. The reason both women spent too much time arguing over not all that much has a lot to do with why Marian never allowed a dog in her house. We know that it's because she hated all dogs because her evil father loved his dog more than he loved her and she was bound and determined to keep that from happening in her own home. She was also bound and determined not to look like the vindictive idiot she was because of a fear of being seen to have a negative character trait. This black-and-white insanity of hers and Elly's is best expressed as follows:

Axiom 1e:

Neither Marian or Elly will admit to doing things for a selfish reason or wish to see a glaring flaw in a plan to 'help' those around them.

This need Marian had to deny wanting to force Elly to lose arguments because she needed to win to make up for her childhood because that made her look crazy would have been bad enough if Elly were an only child. Sadly, Phil's advent only made Elly's feeling that she was unwelcome in this or any other world worse owing to Marian rigidly applying a double standard to keep the neighbours from talking and also because that's just how things were. By hiding behind a boys will be boys ethos because Phil appealed to her for the same reason Jim did, and by deliberately making things unfair because girls had to be kept repressed, Marian helped usher in a world wherein the following problem obtained:

Axiom 1f:

Owing to a childhood where she was always made to be wrong while an interloper she couldn't touch was always right, Elly's default suspicion that she was expected to suffer and be laughed at for wanting to be happy too mutated into a martyrdom complex her idiot mother could never understand.