On this point, they could have at least had Lupita grow her hair out/wear extensions/whatever for this role. She looks more like the Childlike Empress from The Neverending Story than Helen of Troy with that really short hair style & diadem accessory. And it's not like Lupita has never worn a hairstyle that would better compliment the role before, either.
Does this make her look more like Helen of Troy? I mean, no. But it'd at least be closer to what I would expect a representation/facsimile/interpretation of that character to be. Some random Instagram pic of her looks better than whatever she's wearing for the movie.