I'm sure she was required to go, especially since this was the final scene they like to get all the housewives together for. Thought it was rude for her not to say Hello or Goodbye to Kandi though, and the constant bashing of Kandi was a little OTT in my opinion..also rude to leave Cynthia and Marlo there if she was their ride..
Nene has been pretty levelheaded this season so it was disappointing to see her act the way she acted towards the end of seasons 2 and 3. Maybe they filmed that while season 4 was airing and Nene saw what the other girls had been saying about her? That's the only possible excuse for her behavior and the things she said.