I love Regina, but it felt unnecessary. I think this episode made me see why some fans complain about the "Regina-centric" episodes.

^ It actually was necessary in order to help Snow White development as a character in the episode. It was because of her wanting to destroy the people's faith in Snow White that caused the conflict, which would ultimately lead to Snow White finding her inner strength. Plus in the present, it did show the irony of how Regina, who was originally trying to destroy Snow White, was now the one having Snow embrace who she was and no longer being Mary Margaret. It was very poetic and showed how two former enemies end up being responsible for helping each other become who they really are. Regina is no longer the Evil Queen and Snow White is no longer Mary Margaret.

One of the reasons I LOVE season 5 so much is because Snow is once again as awesome as she was back in season 1. I felt like she had become too comfortable as Mary Margaret, similar to how Emma had become too used to a normal life in season 3 and wanted to leave her parents, and it made her lose sight of who she really was. Mary Margaret I feel, while she's not bad, does represent what people didn't like about Snow (Especially in season 2) and she had lost sight of who she was. I feel like that was backed up with how in season 2 she wanted her and David to find their own place instead of going back to the Enchanted Forest. Now she's finally regained her true self, Snow White, and ironically thanks to Regina. What makes great writing is how other characters can be used to help a character grow, especially if that same character helps the other grow as well, which Snow and Regina have done. So showing Regina as the Evil Queen in this episode shows the poetic irony in it, especially when Regina said Snow defeated her in a way no one thought possible, by making her, her friend.

^ Which is exactly why I love the Regina cetric episodes so much. The way their relationship grew never fails to impress me.