hm

No here mom was not a magic-user.
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If her mom was a magic user then there is a chance that her mom might have lived But she died because Athy had a lot of mana. And since Diana can't use magic her body couldn't handle such a strong being inside of her.

Her mother wasn't a magic user but she had a speciality.. It's like Her mother has a kind of unique power but idk exactly what it was.. but it was mentioned before...