I play this game with myself every single day on my drive home from work. Someday I'm going to die, and someone is going to pull the SD card out of my dash cam and hear me ranting about how Reki's attempt to earn salvation was inherently selfish as she was only going it to stop being sinbound, but in the end that selfishness didn't matter because she was actually helping people. Even if she only helped Rakka cope with her sinboundedness in an attempt to save herself, she still helped Rakka. And ultimately that did lead to her salvation, as Rakka was only able to help save Reki because Reki helped save Rakka—oh hey, I'm home