((Prompt: Doing the right thing.))
Rarity crouched on the doorstep of the cloud-house. She did not have versatile magic like Twilight, nor did she have a flying contraption like Pinkie Pie. But she had her means. Moonlight shone silver on her hair as she slowly, carefully pushed the front door open. It wasn't locked, of course. Rainbow Dash had very little reason to ever lock her home.
Stealth was easy in a cloud-house. Her hooves made no sound as the puffy whiteness squashed beneath her. There were plenty of windows to let the starlight in from above. A faint breeze drifted through the openings, bearing the coolness of a summer night.
Rarity slowly made her way through the house, up the stairs to Rainbow's bedroom. This is for the greater good, she reminded herself as she carefully opened the door to her room. It was a grim task, but it had to be done.
On the wall there was a large poster for the Wonderbolts. Resting on the end table was the trophy from the Best Young Fliers Competition—Rarity shook off a faint sense of vertigo from the reminder of that day—and an open copy of Daring Do and the Lost City of the Seaponies propped against her flight goggles. On the whole, a fairly sparse room, occupied primarily by the large bed.
Rainbow Dash was sprawled out on top of the covers, all six limbs stretched out in every direction. A faint snore accompanied the rise and fall of her chest. She stirred as Rarity's shadow crossed her.
Rainbow's eyes fluttered open. “Mmh... Rarity? Wha—”
“I'm so sorry, darling... but I have to do this.” Rarity whipped her hoof through the air, sending a cloud of chalky dust towards the pegasus.
Rainbow Dash sneezed. “Rarity, what the hay? I...” Her eyes suddenly lost focus, and she went completely limp.
The moonlight glinted off of a pair of sharp scissors held aloft in Rarity's telekinesis. “Now you just hold still, darling,” she said, a grin crossing her face, “and let me get to work.”
Rainbow Dash's eyes flickered, slowly drawing open. The light of dawn was only just beginning to illuminate her cloud-house.
“Oh good, dear, you're awake,” came Rarity's voice from behind her. Rainbow found that she was no longer in her bed, but upright in a chair in her kitchen. She twisted to see Rarity sweeping up a pile of multi-hued hair clippings. “Now you can take a look and tell me what you think.”
Rarity levitated a mirror in front of Rainbow. She blinked, peering into the glass. “My mane!” she cried, throwing her hooves over her head. “What did you do?”
“Well, it was getting unacceptably shaggy, darling. I decided it was about time somepony did something with it.” Rarity gathered the clippings together and dumped them into a dustbin.
“Rarity,” Rainbow said tersely, “you could have just asked.”