I remember watching this part in the movie but it didn't impact me as much as it did here because it didn't really give me time to understand the context of Ichi's relationship with Sheila nor the time for me to have at least a semblance of attachment to her as a character.
It's unfortunate that her reaction to seeing her long-time abuser sliced in half was rather...expected. He did it for you, gurl. Even if he had his dick out when you walked in.