They were were the best and worst of sisters. Z has sworn to do better time. Z-978 will not listen when her sister tels her to do stupid things. Because she has learned that she can do that. She can just not listen to the stupid queen.
Diane must make herself smaller, pinker, and cuter. She has a rival and she is not happy about it. But she can't just bite off a significant portion, Train Wreck and Z would be upset...
Both have started suppressing their horn to emulate Surprise. Z actually uses her mouth for things now, Diane cheats... constantly.