@YyuukiZzero I'd agree that that could be part of it at least. This whole time, she's been suspecting Shino wasn't really thinking of her as family or something along those lines, but in reality what Shino was keeping to herself was this. Relief to find out she was wrong, but also guilt about thinking all of that while Shino was in fact doing not much other than focussing on how best to give Nozomi this memento. Then could come the guilt you mentioned, because she's been given this think to remember her lover by, but her fixation on Shino sort of stole its thunder.
I'm really not sure I trust my gut feelings on anything with this series too, though. Might be reading more into this than I need to. I've noticed I often give these manga authors waaaay too much credit for thinking ahead, and then they pull the rug out from under me like "Actually, I never thought that hard or that far ahead about this at all. Here's what's actually happening in the story, and it's kind of dumb."