The really repulsive thing is that she shares another annoying habit with her parents and brother: she can warp history to suit her prejudices as events unfold. This, of course means that she probably does believe that her on-again, off-again dalliance with Anthony was the grand, sweeping romance that some of Lynn's more cringe-inducing fans believe it to be; this can be lumped in with her belief that her childhood did not suck rocks and that she was a misunderstood genius in the category of lies she tells herself.
That being said, it's not just her own past that she rewrites to suit herself. Let's, as a for instance, look at her first encounter with the sitting duck antagonist she dares to despise. To explain why Liz took an immediate dislike to Thérèse, you first have to understand a fact that Beth Cruikshank is unaware that she divulged; without intending to, she revealed that the woman that she and Lynn think of as a reptilian monster is actually a fragile, insecure woman with a need to prove herself worthy accompanied by a fear of being forced to not only accept the humiliation of being cheated on by an entitled patriarch but to trade away her dignity as a human being for cheap baubles. Mrs Cruikshank also accidentally made a point of making all her dad's mistresses vapid-seeming blondes who all look just like Lizardbreath.
What distinguishes Liz from actual gold-diggers is that she doesn't know what she wants, she has no idea what other people are thinking and she has a lack of opportunism that almost amounts to a lethal mutation; she also cannot understand that just because she wants to be friends with Anthony, that doesn't mean that she should as well as failing to see that while her intentions are honorable, his reaction isn't and that THAT constitutes a problem. The second Thérèse tried to explain that Liz represented everything that she feared would happen in her own marriage, her doom was sealed; instead of doing something that took time, effort and the ability to see that she wasn't the victim, the whinging little twinkie edited the conversation so as to turn a terrified potential friend into a cold-hearted bully in order to avoid having to admit that she might not only be in the wrong, she might actually be the bad guy.