Considering how loud his proclamation that he was going to go buy something was I'd be shocked if Moe and Nyaa didn't realize that Ichikawa was there despite them apparently not noticing him on the first page. And then Yamada gets up a minute later and goes after him. They probably started to at least suspect that Yamada was crushing on him here.
@Suzushiiro I dunno, dude. They know about her food habits, and she went back for her wallet when her conversation excuses flopped, so her journey for the food she likely came back with eventually became more prominent. Could've just seemed like classic Yamada to them.
Looks like her breasts start getting bigger right around here. She was fairly normal for her age at the start (aside from her height), and she's super busty in recent chapters. Puberty hit her hard and fast.