@pockettrash If you mean the queue thing, waiting in line for a long time on your first date, while not having many topics (or being too nervous to talk) can make things turn badly.
If you mean her reaction though, it's because she's saying that their relationship is not being made worse by staying in line, so she's kinda implying there that they are on a date right now.
I just realise that Yamada is basically saying that they are still having fun even if they wait in line and basically admitting that they are on a date.
Huh, honestly took me a bit to understand what Yamada was saying and why she reacted that way. Can see why Ichikawa wouldn't get that Yamada almost admitted that this was basically a date for her.