The relationship axioms.

As one could expect, Elly's inept attempt to live up to her mother's example as a homemaker and parent is part of a wider problem that makes her life worse. One of the most egregious examples of this tendency took place when Liz was trying to get her to work through a word problem; instead of doing the mental arithmetic, Elly focused on what the person was supposedly doing and condemned him for doing it. When we factor in how her love of gossiping collides with her trouble with getting facts straight and watching Jeremy's insane motive for trying to dismantle April wash over her, we're stuck dealing with the following limiting factor:

Axiom 1r:

1) Owing to a fixation on non-issues and poor listening and comprehension skills, Elly almost never actually seems to know what's really going on around her.

2) Elly does not realize this.

The reason that this makes relationships harder than they need to be has a great deal to do with her conviction that she's the only person around her who cares to stave off the chaos and ruin she fears. She can't allow people to help on their own terms because she can only admit to one way of doing things and she can't bring herself to trust people when she can't see them because she has trust issues. This leads us to:

Axiom 1s:

1) When forced to imagine what people are doing when she isn't present to stave off chaos and ruin, Elly's self-pity and megalomania lead her to assume the very worst.

2) When confronted, Elly says that she trusts people but not situations.

Since she doesn't trust people not to make her life worse and since she's not very observant or smart, she tends to assume that she has to be watching her family non-stop to keep them from ruining her life and laughing at her misery. Mike can treat her like she's his servant, John can be a pompous oaf teaching Mike to do that, Lizzie can be clinging to her like a barnacle and April can drive her batty just by breathing but as long as their bad treatment of her is simply emotional and not physical, they're great people. If someone were to love someone other better, they would be dead to her. This is owing to two more traits that make her life stupid.

Axiom 1t:

Elly is obsessed with being loved most of all because she assumes she's loved not at all.

and

Axiom 1u:

1) Elly firmly believes that one MUST be in an exclusive physical relationship to be taken seriously as a member of society; those who are not are clearly a threat to established relationships as that's what romance comics told her.

2) Physical disloyalty is the worst thing a person can do to a partner and the cheater and those who do not call for his or her destruction are vermin who seek to destroy the world.

This is why Anthony gets a free pass while Therese is filth. While he decided that his marriage was over, the closest he came to doing what literal-minded dimwit Elly thinks of as cheating is asking Liz to wait for his marriage to implode.