Four years after Spike left for Canterlot, Rarity hears word from Twilight that the dragon is returning to Ponyville. Her excitement is obvious, being able to reunite with a very dear friend of hers, but this message returns certain memories and dreams to the elegant mare.
She knew why he had to leave, was able to see it in his emerald eyes every time he looked at her after that day. Rarity was prepared for a reunion like this; it was clearly going to happen eventually, but she had no idea why Spike would return now. No, that wasn’t true. The mare did know the why.
After all, it was her who had caused him to leave in the first place.