Clytemnestra and Helen of Troy are two sides of the same coin. Clytemnestra killing her husband is a parallel of Helen of Troy's visible disdain for Menelaus in the movie. Both women are trapped in marriages with power hungry men.
Both women shows what happens when you want to end the relationship. Helen ran away with Paris and was unsuccessful; Clytemnestra took a lover and killed Agamemnon to avenge the murder of their daughter.
This is probably why Nolan decided to have Lupita portray both. Their marriages are so similar. Plus two sisters being married to two brothers come on. I know an issue with a lot of black viewers is that they had a dark skin black woman in an unhealthy relationship, but Lupita did such a good job portraying both disdain and grace in both roles, it kind of makes sense that Nolan cast her.
Now if you're a fan of Menelaus and Helen having a happy marriage, sorry that doesn't happen in this movie.
Now there are a lot of people who think that Helen may have scarred herself instead of Menelaus doing it to her. The main evidence they have for this is that she apologizes to Penelope for what has happened. But there's another element to the story that people rarely mention. It's a fact that her sister's daughter, her niece was sacrificed, for winds to sail to Troy. And if she knows Clytemnestra killed Agamemnon, then she most definitely knows why. Perhaps it was a self-imposed punishment for indirectly causing the death of her innocent niece









