Not sure about that first name, as El isn't really a name AFAIK (though it is Spanish), however Elle is French so...¯\_(ツ)_/¯
Nobody names their daughter "Elle" in France ; that's be like naming a child "She". Also, it is illegal, here, to give stupid names to your kids. Anyway...
Based on "Andalusia" being a spanish region, "Viridiana" a female character from a spanish movie (italian name but probably picked because of bunuel's movie), the name and blueshirt + rig pointing at the "División Azul", and approximative european culture grasp of the average japanese combined with a bit of "fuck that"... I'll take a chance and say the spanish "El" might be the right version ; as it could have been taken from the famous "El Cid".
(maybe i'm "prying unlocked doors", my japanese isn't good enough to read pixiv stuff)
Surely is "El" (not to be confused with "Él", personal pronoun for "he"). I don't know who would pick up a Spanish article like "The" as a name though. Couldn't they pick up "Ella" ("she" pronoun) or at least "La" ("the"'s single feminine form)?