Iirc WN explains the main reason MC's mother left was over the longevity difference between her and Edmond (although this isn't to say Analia couldn't have brought it up in an argument). She didn't want to see him suffer as she aged and died per her human lifespan, while he still remained young.
That said, Analia will eventually get over it once she sees how determined and spirited Haru is, just like Edmond.