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One of the aspects of Isayama's writing that I appreciate the most is his ability to re-contextualize past events and change their impact on the story and the characters. This scene was already great, but it's even more meaningful for both Eren and Historia after #aot130. 
To properly understand Eren and Historia's exchange in the flashback scene, is important to analyze the duality of Historia's character. She's constantly struggling between meeting other people's expectations (her Krista persona) and acting according to her own wishes. #aot130
Historia initially rejects Eren's plan and states she's willing to go with the Military Police's idea of sacrificing herself and her descendants for the future of Paradis. That's what any "good person" would do, right? That would be something she could be proud of. #aot130
But Eren knows better than that. He saw the real Historia back in the Reiss cave. He knows that deep down inside, she hates the idea of being turned into cattle and being eaten by her own children. That's why he won't allow it. #aot130
Eren reminded Historia that she's "the worst girl in the world" and that she saved him because at the end of the day, even if she pretends otherwise, she wants to be able to live her life freely. This makes her "selfish" like Eren and, by extension, and enemy of humanity. #aot130
After hearing those words, Historia is no longer able to lie to herself and oppose Eren. She wants to live and since he' the only one on her side, she will be the only one on his as well (Sorry Floch). Her having a child will give Eren enough time to cause the rumbling. #aot130
