Gabby: And…I know what it's like to miss that now too.
This shows that Gabby is forgiving of Rarity, and that she understands why she missed Spike(different reasons but from my perspective, Rarity see's Spike as a little brother, Gabby see's Spike as her best friend. Sparity to me, is an incredible friendship like Dipper and Wendy, Dipper means the world to Wendy, but not in a romantic way.)
Honestly I think this did more to give Rarity character development than de-evolve her like some would say. In the words of Twilight herself
Twilight: Friendships change. But just because Spike made a new friend, doesn't mean he'll stop being yours.
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