So Blair finally saw her relationship with Chuck was toxic and she didn't like who she had become with him. I think she was right to walk away.
Jenny, Jenny, Jenny ooh, you know all of this is going to come back on her and Nate will not be too happy.
I bet there is a very simple straightforward reason for Lily being with (as we're led to believe) Serena's father. Maybe he's not well or something? We know she loves Rufus, so she's not cheating on him.
I loved the scenes between Darota and Blair.