This, I should think, is due to the regrettable fact that Elly seems to me to share her creator's distinct difficulty with remembering things. The same mental peculiarity that can't keep track of character histories in the real world is the same one that allows Elly to forget that her children exist when she isn't looking at them. Also, given that Elly is sick with a persecution complex that makes her see every little thing as part of some vast conspiracy to keep her down and prevent her from ever being happy, asking her to keep track of her kids is seen not as helpful but as an attack and a sign of hatred.
Worse still, the difficulty she has in dealing with one child isn't doubled when dealing with a second. Instead, that difficulty is multiplied by itself when each new selfish, chaos-loving monster who wants to destroy her because children hate adults because their inherent love of chaos makes them believe the evil lie that what happens to them matters and so on through the paranoid ranting is added to the mix. This means that Story Time at the library isn't going to be the quiet, productive experience it should be but instead an hour of screaming, threats and angry, passive-aggressive whining about made-up sins by a woman with no empathy, common sense or fair play in her.