
I think we have to wait and see to be sure, but I think she's been in a sort of denial about her husband's death, the same way Shino was. I think she's been letting Shino sub in for her husband, and hasn't really processed her loss. Being presented with a ring that he wanted to give her but couldn't? Having Shino do it on his behalf, when it's something he would clearly would have done himself, brings home the reality of the loss in new way, that makes the pain fresh.
I mean, I've been there. When you lose someone, particularly close family, there's a lot of moments of realization like that, where the loss suddenly feels real. Holidays and special occasions are landmines. As are familiar shared spaces and daily tasks.

perhaps or perhaps the answer lies somewhere in chapter 74...
Nozomi is always doubtful in averything. she always needs to be sure and she doubted in her own feelings wen she says "i enjoyed" and in words/feelings Shino. but at the end of Chapter 74 Shino directly said what exactly she feels :) in 76 Nozomi stop doubt.
It's hard for me to explain because I don't speak English very well ⁄(⁄ ⁄·⁄ω⁄·⁄ ⁄)⁄
I feel like when Nozomi said "So it's true" she means that Shino has moved on ahead without her... but that could be wrong. I'm going to read some chapters again to see what she actually meant.