One time I heard Skinny call Chunky what sounded like "Deanna". I know that's not much, but it's enough for me to vote with you.
Skinny = Ana
Chunky = Danna
As far as the actual events of the cheating, I don't think we'll ever know for sure. But one thing for sure is the phone texts. Ana has spent quite a lot of time going through Danna's phone...she even seemed to be reading texts to Danna's face while Danna stood there taking it. Now, I'm not criticizing Ana, but damn...she really raked Danna over the coals. Of course, Danna deserved everything she got.