What would make more sense is for Liz to look back on the past and remind herself of why it was that she could never really come to Elly with her problems. As we know, Lizzie is going to spend the next decade or so feeling insecure about her looks and hoping and praying for the day when she no longer looks in the mirror and sees someone dumb and ugly and unworthy of love. She can't come to Elly for the reassurance Mommy offers up because she remembers something Elly doesn't: Mommy's habit of looking in the mirror and baying at the moon about how ugly and old and fat and unworthy of love and happiness she is.
This is why it is that Elly gets blindsided by the fact that Liz doesn't go to a delusional hypocrite when she wants to be told that yes, the feeling of loss and inferiority will go away someday. She can't go to John because she gets told that she's a bad person who can't care about great big things she can't do much about if she shows the least bit of concern about little things she can do something about and she can't go to Mike because his paranoid dread that he's going to sent away to a farm because they like the cute little girl best makes him act like a rat-fink so it's time to turn her back on all the love in Elly's junk heart and talk to a stranger.