Hm, I don't usually empathize with the characters much while reading fiction since I prefer keeping my own thoughts and feelings separate to avoid coloring my expectations of them, but this was a case where I could really understand Adachi, more so than usual. Although she herself reflected earlier on about how empty her life and person are without Shimamura, so I'm not sure how healthy it can be to just accept she's not interested in ever opening up to other people.
If that girl with the glasses who seemed to know Adachi is someone who already appeared, I can only think of that middle school classmate who was with her on library duty.