Thanks for the chapter, Silas.
This has been pretty well foreshadowed that she more than accepts her coming death, and doesn't really believe in the repair plan. It's boring if everything always works out for the MC, even if it's a cheat isekai. It keeps things interesting and progresses character development.
The real complaint should be if she survives, which is much more likely for this genre.
To be totally frank, I don't really care if Sheena dies; I've been totally detached from her character from the moment she showed up--which can be said of a number of the new residents of Ichinojou's World, including a certain old one. However, I do disagree with--as I long have--with the idea of likable character death to build gravitas or force weeping. I've seen it happen so many times in stories, and each time it was only to make people wax emotional--and each time was an assertion of a concept I've emphatically repudiated for as long as I can remember: that a story only has value if it's miserable, bears some kind of misery, or is otherwise negative.
Things already haven't worked out perfectly for Ichinojou, but he's been able to overcome his obstacles nevertheless. I don't see a problem with this, and it's telling that many people (I am not referring to you, mind) today only see quality in an MC who not only struggles constantly, but
loses or is placed in a losing position frequently. There is surely a difference between an MC boringly given constant, effortless victory by the author and an MC who always wins--but works to do so.
Sheena's death doesn't bring anything at all to the story, just darkness and grief. It was set up well enough, but I don't remember anything that
necessitated her self-sacrifice. Her death is, as of this chapter and as far as I know, pointless, and her staying dead would accordingly be meaningless. Therefore, if Sheena survives, I would not mind it.