This bizarre mental defect seems to explain why she treats the children the way she does. As by way of example, we find ourselves noticing that ten year old Phil probably looked a damned sight like Mike does. What this means is that Elly doesn't really see Mike as being a person in his own right but as somehow being an extension of Phil's life force come in to once again make her life worse and keep her from winning anything. This means that Mike has to be made to live the life she wanted Phil to live in order to keep Phil from winning again.
This, I think, also explains the way Liz got steered into a teaching job she's not really suited for. Elly looks at her child and sees herself and thus wants to give this new extension of her soul the life and career she was denied. She wanted to be what would probably have been a very lousy teacher and she made sure that Liz was Lynn's idea of a great teacher (which is, of course, a horrible failure of a teacher who cossets a selfish attention hog who delights in sabotaging those actually willing to learn) and married a wussier, more gutless version of John.
Finally, we come to the fact that she cannot see herself in April at all and thus regards her as being an alien whom she cannot relate to. As I think I said long ago when I think I talked about this before, the reason Elly can't relate to the little stranger that she never grew up with is that we're dealing with a very dull mind that doesn't like to step out of a comfort zone. Rather than get to actually know her children and realize what's really best for them, Elly stupidly decides who they should be based on her own childhood. The end result is a lousy author and horrid teacher who convince themselves they're happy because it makes Mommy happy that they're misfits who can't function.