There are two points at which Daisy and Gatsby's relationship could be considered "new". First, it seems that their "new" relationship occurs as Tom has become enlightened about their affair. It seems as if they are happy to live it out loud right in front of him. It's not as if he hasn't been doing the same thing to Daisy. This seems to give Gatsby a greater boldness to make comments throughout the chapter.
The second "new" to their relationship occurs after Myrtle has been murdered. At the end of chapter 7, Daisy goes into her house. We don't know what occurs in there, but the audience can infer there is an amount of reconciliation going on. Many emotions must be flooding through both Tom and Daisy's heads. Gatsby is oblivious to this fact and acts as a peeping Tom making sure Daisy is "okay". What he fails to realize is the fact that he is what made things in her life not okay for a time. Thus, their relationship at this point seems one-sided. If we were to see what happens next between Daisy and Gatsby, she would likely break things off with him.