They both were just walking to the pack house but Athena kept observing Dean because the way he kept zoning out... And just not at all try to talk made her suspicious about something.
Because he is someone who talks a lot but this time, he is only calm and just kept walking without talking anything...
She is sure that he will talk anything to even make Athena forget about her thoughts but he is not even trying to talk about that but only kept thinking about something that doesn't make Athena any sense...
She can clearly read his mind but she doesn't want to get into his privacy that every one has. And Athena knows that Dean would tell her what is bothering if not now or later... But he will surely tell her. But this time, it doesn't make her feel good but it makes her feel like he doesn't at all want to talk to her about anything this time.