Ei was not a mother. She never was and never will be, frankly.
As far as I'm concerned, Makoto was my mother. Ei may have created me, and Makoto may have been dead at the time of my creation. But I was modeled after Makoto. And took after her emotional nature. Ei was far more like an aunt who gained custody and was far too unstable at the time to actually care for who was technically a kid. At least Miko was there to prevent Ei from doing anything too drastic. Too.. deadly.
Now this is not to say I hate Ei. I don't, I've moved past it. And I can understand she was very very badly handling her grief. That doesnt mean I forgive her ofc, but whats done is done and it cannot be unwritten.. as I learned the hard way.
Ei tried to be better later on. When Nahida encouraged me to reconnect with her and Miko for closure. Yet she was never a mother. And never wanted to be one. She was and always will be just a creator. And I don't mind that.
And I don't think any Makotos would dislike that I claimed her as my actual mother. I like to think she would be very proud of me, and touched by the thought. Apologies to any Makotos reading if I'm wrong about that, but I'm sure you understand.
~Wanderer 🕯♟️ (Genshin Impact)