Board Thread:General Discussion/@comment-27738735-20150928215717/@comment-28799866-20151003045657

Heeha wrote: Yowhatisuppeeps wrote: Dipper ans Mabel are not getting along as well as they used to.... I kind of suspected this. Mabel's kind of been acting like a jerk lately. I don't think she learned anything in "The Last Mabelcorn".

I think it was the "morality is relative" part that made her NOT care about morals. Also probably this episode has the morals too.