I have picked up on this on air flirting as well. He has mentioned her before in the past (Pre-divorce) but he seems to talk to her and make references a lot more.
I too have noticed that he talks about (and to) Dawn a lot, but I think he does that because she is the only female staffer in the place. As such, she is more likely to get softer treatment than would Mr. Snirley, Bryan, Mr. Winterble, HR, and the others.