I think it’s basically that Cora screwed her up. She never had that close mother/child relationship with Cora, and then she had a step-daughter who she hated forced on her, so she became fixated on having a child she could love the way she’d always wished her mother had loved her.
I agree that giving her a long lost bio-child would feel too much like they were trying to give her a Henry replacement. It could be a good twist if she’d found out she was pregnant after Daniel died, but then she miscarried, though. Something like that could fuel her desperation in wanting to have a child.
[adrotate group="5"]