Fluffy Buns(Flurry Heart)really is a flirty one!! Of course Lapis had no idea who that attractive unicorn was.
Lapis moved to the Crystal Empire in order to study with Sunburst, thanks to Starlight. They used to spend most of the night on the library and Flurry found them really interesting, so she decided she coukd have them for herself. Lapis was pretty recessive to her "friendship" attemps as Fluffy Buns, but found themselves really enjoying her company, she was intelligent, she was funny, pretty, brilliant, until she decided to present herself as Princess Flurry Heart.
Of course they were really recessive again to her friendship, but Flurry was too determinated. It was wrong, Flurry was their mentor's protegee, they just couldn't do it. But they did anyways. When the whimsical princess got bored of her new adventure, she decided to finish it, it was not fun anymore, too easy for her. So bad she found herself missing the nerd.
Lapis ended up been her mainstay on her life, giving her the stability she needed. They also began to help her with her royal duties, making her load less heavy.
Neither of them will say they are a couple, they're not even officially dating, but they sure have fun together, they support eachother, and they make the other one really happy.
But remember, they're just friends.