But the other choice was this: that she might return to Middle-earth, and take with her Beren, there to dwell again, but without certitude of life or joy. 【Then she would become mortal, land subject to a second death, even as he】; and ere long she would leave the world for ever, and her beauty become only a memory in song.
我觉得这是对她命运的解释,而非她血统的解释。
至于她的儿子Dior,宝钻里有这样的描述:
Then Dior arose, and about his neck he clasped the Nauglamír; and now he appeared as the fairest of all the children of the world, 【of threefold race: of the Edain, and of the Eldar, and of the Maiar of the Blessed Realm】.
你按照半精灵对命运的选择去推理的确可以得出Dior就是凡人的结论,但问题是,半精灵(Peredhil)的定义是从哪里开始的。我在宝钻里只看到从爱隆和爱洛斯开始,提到关于命运的选择,也是从他们俩开始。
Bright Eärendil was then lord of the people that dwelt nigh to Sirion's mouths; and he took to wife Elwing the fair, 【and she bore to him Elrond and Elros, who are called the Half-elven】.
这是关于选择命运
The Valar indeed may not withdraw the gift of death, which comes to Men from Ilúvatar, but in the matter of the Half-elven Ilúvatar gave to them the judgement; and they judged that to【 the sons of Eärendil should be given choice of their own destiny.】
也并不是可以这样确定爱尔温和迪欧没有选择权,但毕竟她母亲是十足的精灵,而且迪欧可能还没选择就被杀死了。