Natasha i can see as Eladia, in my mind Nina Dobrov is always young Lanfear, the Selene one. She'd have to get rid of the American accent i guess since the show has no American accents in it.
I'm a wondering who will be the flame haired fiestyness that is Aviendha.
I can't think of any apart from rose leslie and she maybe OK.
I forgot Eleanor Tomlinson
Lily Cole
I've seen other possibilities in an image search, but I don't know the names. I guess they need to be under 30/20