It could have been worse. It could have been a *lot* worse. Rarity could have actually been called out on her lies, or Twilight could have been angry at her for not doing what she promised (although I think that would have been out of character for her). It actually picked up a lot once the characters other than Rarity showed up.
Still, Rarity as Worst Pony overdose. On a scale of one to ten, I'd give it a 'it wasn't objectively bad but OH THANK GOD ITS OVER'.
Let us never speak of this again.