The problem is that usually, once Elly is no longer associated with a person or a thing, that person or thing tends to vanish. Once she was let go from the library, it was if a great force scooped it up because she never went back there. Once Mike stopped playing hockey, the only time the rink was mentioned was so Elly could complain about how tax dollars were wasted on sports and keeping our infrastructure from crumbling. Once Annie was left to fend for herself, it took years for her to show up and explain why it is Elly was stupid to ignore her. Once Fiona was squared away, she vanished into the ether. Once Mrs Dingle had her heart attack, she might as well have been put on an ice floe. It's as if Lynn has an aversion to revisiting things and people she's outgrown.
What this tells us is that when April went out into a wider world, it would be as if she were never there in the first place. Instead of the expected hand-wringing about how her poor misguided child failed to see the great big love Elly only thought she had for her, we'd be dealing with her having to be reminded that she had a third child at all because she can't remember things she's not actively dealing with.