In the book, what is the point of Liir?

I’m struggling through my third attempt to like this book. Love the first part the ends with her entering the mauntery. Absolutely love it. But when she leaves the mauntery it just seems to go off the rails. I’m really struggling with Liir just sort of randomly appearing and Elphie offhandedly saying that she was basically in shock from grief for her first year there and must’ve given birth to Liir during that time. I’m willing to suspend an awful lot of disbelief for this book, but that is too much. If you want Elphie to have a child with Fiyero, that’s fine, but there must be a hundred better ways to write him into the story and set up his relationship with Elphie.

Is there some deeper symbolism that I’m missing? I’ve never been good at literary analysis. Does this bother anyone else?