Board Thread:General Discussion/@comment-25926288-20161128015930/@comment-24674051-20161205164049

Honestly, if you look at Regina's actions, she first steps in and saves Zelena, then she takes her back into the farmhouse and heals her magically. As others have noted, if she was truly reverting, she would not have done either of these things.

I think holding the grudge is meant to be the writer's expression of the fact that Regina has not completely moved through the grieving process for Robin, which in turn sets up the scene at the end of "Wish You Were Here". Regina is still very much hurting, and the events that led to Robin's death were precipitated by the TLK administered by Zelena to Hades, so Regina has mentally reassigned blame to the one person available that she considers a part of that tragedy. Never mind the fact that Regina encouraged Zelena to pursue the relationship (at least at one point), and that Zelena had nothing to do with Robin, and stepped in to save Regina herself.

The scene in Changelings simply points out the fact that Regina is still greiving and not thinking clearly about the events surrounding Robin's death. (a fact that is underscored in the beginning of "Wish You Were Here").