not really commenting on the first bit since i think we just disagree about what is in the realm of normal for this series but specifically for the "maybe she thought..." bit, I generally agree with you, but we're speaking about this from an objective outsider's perspective. If we're giving the author some credit, the logic of "i know my abuser is about to do something but wouldn't this put me in more danger and who would take me seriously" is a real thing and this logic is compounded by the whole rich sugar daddy that already weaseled them out of hot water. Not to mention she is a part of that group doing the illegal activity which adds an extra layer to the self-preservation thing. In other words, long-time abuse victims tend not to be the best at viewing their situation from outside perspectives.
Part of this is not wrong... but a lot is.
I was saying that this didn't really earned her a redemption because her actions are basically meaningless.
Without the Deus Ex in the form of crumbling staircase, which made absolutely zero sense, this evidence collection would have been wasted completely. At best, she would have delivered it after the noble had obtained Rain and probably traumatized her for life. Assuming they even got her back. Assuming, as I said before, that she even got the courage to act then.
What
did earn her a bit of redemption was her casting a spell on Clover to slow the fall when the staircase broke down. And then preventing Simon from ruining the escape. But that's completely unrelated to the evidence collection. This letter only brings her a little sympathy as a kind of victim... which she was really not.
Yoke was the abuse victim and she was a bystander who didn't dare to raise her voice because she needed the job. That's fine, people are not all strong enough to sacrifice their life and job for others, but that doesn't make her a victim. (At least not in light of what we know in the manga. The novel might be different but it's not in debate here.) Also, from the actual victim's perspective, she was as much an abuser as the others.
So the collected evidence simply was a pointless endeavor without the unpredictable (and logically impossible) circumstances that let it become useful in the end. Based on what she knew and did at the time she collected it, that was at best a way for her to assuage her guilt a little. In character, it was not meant to be helpful to Clover. It was a storytelling device, which is a reason based on the required (and flawed) flow of events, not based on character motivation.
And that's why I mind it. Because it's meant to garner sympathy for her that she didn't earn (at least not with this). She earned a bit of sympathy with her actions in the dungeon, but everything she did before then was devoid of meaning. This letter didn't get a single tear of sympathy out of me.