What a chapter indeed. Kishimoto will forever remain my favorite author.
I do wonder what happens though. How could she have died from that, if he said you let her die. If it was from that, it would've been murder or an accident. As for the mistranslation theories, if he said "You killed Rin" a couple of chapters back, this one would have little impact because we would've known Kakashi killed her before seeing the final page of this week's manga.
So I do believe he meant to say, "You let Rin die."