The reason that I mention Dee is that yet another of Elly's irritating tendencies has been faithfully replicated by her daughter: drawing the wrong conclusion when observing something and sticking with it. Elly moves the dirt around and thinks being a mother means saying no to any request her kids might make because she doesn't understand what her mother was trying to do. Liz appears to have learned the wrong lesson from the lead-up to Phil's wedding. As you know, Elly made no effort at all to learn anything at all about Georgia because Lynn had no real curiosity about her own sister-in-law. Granted, Lynn does have the advantage of knowing the woman's maiden name but that really doesn't matter in the grand scheme of things. What does matter is that Liz has it in her head that she shouldn't really get to know much about potential in-laws because Mommy didn't and she wants to be like Mommy so Mommy can love her and pay her attention and say she's glad she had her and hey, presto, there's another way Liz is like Elly.
Not only did this give rise to the annoying scenario in which she chickened out of meeting Paul's folks because riding in helicopters is cool and meeting potential in-laws is cruel and scary and horrible and why she cramped Mike's style growing up to be a petty little fool, it (and assuming that she has nothing to say to an older woman because she's got in her fool head that playground hierarchies matter in the adult world) is why she never treats Deanna as a potential friend or mentor. What she sees is a form of superior servant whose job it is to tend to Ugly Brother while he is being more loved than she is. My guess is that her acting like she's in grade five and someone is trying to be friends with a friend and make him have to choose is also why she didn't have a sweet time talking to Therese.