I really doubt her statement about her impression of Nanase was intentional. I think she blurted it out because she's freaked out and talking faster than she's thinking. It also explains why Nanase's experience with Elliot was a factor in her initial interest in him.

Honestly, Diane's taking her first taste of the Shive lifestyle fairly well. She went to get help at the first sign of oddity, has kept her head despite getting (justifiably) panicked. She also hasn't tried to pull her usual Alpha Girl play, opting instead to leave the experienced members of the group in charge. And yet she's also asking good questions and challenging questionable decisions.

This is good, because Rhoda is already a pawn in Pandora's game. Diane would not have been able to avoid the Shive lifestyle indefinitely, and with Jerry in play this is probably an almost ideal introduction to it. Much better than Susan's, definitely.