So basically what you’ve got going on here’s that Amore has been brought back by Sombra, Hope, and Zecora (in the Neoverse, Sombra fled to the Everfree forest bc so many ponies hated him). Twilight takes it upon herself to help Amore get integrated into modern Equestria (yeah, like Rockhoof- except she won’t end up wanting to die as a result of the help).
 
Of course, being Twilight, she decides the best ponies to do so are her friends. One by one she goes to them, hoping it’ll just kind of click.
 
But n o. Pinkie Pie, while endearing, was a bit too touchy for Amore. Fluttershy was preoccupied with planning her own wedding. Applejack was just far too busy, yada yada yada.  
Finally, Rarity was the last on the list. Twilight didn’t see this working out, and thought Rarity might make Amore uncomfortable with her theatrics.
 
Turns out (because this is me, uncreative as ever) she was wrong. Rarity and Amore hit it off immediately. Rarity helped Amore recover from her past, and Amore helped Rarity learn the traditional Crystal Empire hairstyle (I’m downplaying it, of course). SHIPPING!
 
Nowadays you can find them braiding eachother’s hair and talking about how proud they are of their children and how much they love each other- plus more stuff that makes the kids groan in discomfort upon hearing.