I read it about a year ago but forgotten the title. Basically it goes like this, as far as I can remember : The girl was having a conversation with her friend at the restaurant, then the FMC accidentally dropped the glass she was drinking, but her friend said it's okay since it will turn back at once it was, and it did. Then she had a quarrel with her friend later on in the story, accidentally killed her, but the FMC was shocked that her friend revived, or at least "turned back into once it was" and then she leave the town.

Well never mind. I found it. It's ** Nakushita Mono wa Nandesuka ** by **Barikios **