Rarity dreamt of a unicorn mare called Amethyst Wind.
Amethyst reminded Rarity much of herself when she was younger, full of vibrancy and desire for adventures. She was several decades younger than the elderly Rarity, and unlike Rarity, Amethyst Wind was not cursed.
"She's beautiful, isn't she?"
Rarity looked up from her book, smiling at the mare sitting opposite her, busy burying her face in her hooves with what could only be described as a love-struck expression.
"I remember being quite in awe of her back in the day, yes," Rarity said, turning back to her book. A memory of long ago came back to the surface, of a flustered unicorn having confessed her feelings to an equally flustered alicorn.
Rarity had learned to suppress that memory.
Amethyst giggled. "I always forget you used to go to the library when you were young. She barely speaks of you." After a moment, a blush shot through her face. "Er. Wait. That came out wrong."
"That's all right, darling."
After all, Twilight barely spoke of Fritter Cobbler.
There were many things Amethyst Wind did and did not know. She knew her mentor had stopped visiting Twilight due to a terrible accident decades ago that was responsible for the scars on Rarity's leg, though she did not know it was also because her mentor was cursed. She knew Twilight Sparkle and Rarity had once been friends, but she did not know they had once been in love.
Rarity had never said anything, and neither had Twilight.
An agreement that was made in silence and would stay silent.
"I think she likes me," Amethyst said, and in her voice rang a feeling Rarity had not experienced in a long time. She giggled, and whispered, "I think Twilight loves me, actually. Maybe. I hope. I want to talk to her all the time, but I can't! Uuuuuugh!" She groaned and buried her face in her hooves. "Why can't I be with her all the time?" She giggled at the impassive stare Rarity fixed her with. "Sorry. You must think I'm silly."
Rarity laughed. "Hardly, darling."
With her magic, she levitated a jewelry box from a nearby shelf, and placed it on the table, right between them. Carefully, she opened it up, extracted a broken necklace she'd not touched in a long time and floated it over to Amethyst.
"Take this to her," Rarity said with a soft smile. "She'll understand."