Evey genuinely didn't notice before. Not consciously anyway. When something might have occurred to them it didn't quite register. But to be fair, Evan often kept his distance from Evey. So they haven't had that many interactions. Even before the Museum, they barely hung out together. Though back then it was only by chance and had nothing to do with any bad blood. 

Evan's finally getting a chance to speak his mind. There's a possibility he can't get around to everything he wants to say though. But he'll sure give Evey an earful.