I think the way Shimamura now doesnt hesitate nearly as much and actually tells adachi of her plans when going out to meet someone, and not stepping around the topic because she knows how sensitive adachi is, is really good
It shows shes not stepping on eggshells anymore and is treating adachi normally, shes trusting her a lot more with not freaking out about normal things, and adachi also is not freaking out about normal things either.
You gotta remember, if this was 30 chapters ago and shimamura told her she was gonna meet with a friend, adachi wouldve either had another phone call break down moment or followed them like a stalker or something (not actually, but she would be doing a lot of mental gymnastics)
+ And also how easy it was for her to mention that she was in a relationship to tarumi. Instead of spending pages monologuing just "tarumis perspective of me will change and uncertainty and talking to people and adachi and etc etc"
She's serious about Adachi