Avan's gobsmacked stare continues, now accented by his face getting redder and redder, as he tries to figure out how he's even going to respond to this. He can definitely see how Popp reached this conclusion, even if it is the wrong one. In theory, it's an easy misunderstanding to clear up. Avan doesn't talk about girls because there's just the one he's already completely smitten with...

...and the fact that Popp doesn't already know that is proof enough that things didn't work out between them, and that's just the best-case scenario. It could mean something worse, as much as Avan doesn't want to think about that. And Popp's not stupid. He'd realize that just as Avan has. And then he'll feel like a total heel for bringing it up when he was just trying to lighten the mood and be supportive and auauauuuugh.