Karen may work very closely with Matt and Foggy, but they keep her in the dark about the former's 'little secret', namely that he is the Man Without Fear. Based on Karen's guilt in this trailer, and the way she specifically mentions Daredevil alongside that in a conversation with Matt, could the trailer be hinting that she is now in the know about his secret identity? Matt's quick "there's no connection" suggests otherwise, but it would certainly make sense for her to know, and it'd be a major surprise if she didn't find out at some point in Season 2. The secret identity issue is something many superhero shows struggle with - The Flash has badly handled it on a couple of occasions in both Season 1 and 2 - and hopefully it's something Daredevil can avoid becoming a problem, especially when it comes to the love interest.