Rarity’s room belonged in a dollhouse, with everything so neat and tidy it looked like no one had ever set foot in it before now. Dash looked around and noticed one of Rarities armoires was ajar. She stood before it and threw the doors open, surprised to find a computer display as long and tall as a mirror, displaying real-time footage of her as she stood before the device’s camera, perplexed.
“Welcome, Rarity. Initializing trial mode. To abort initialization, please speak the password before the process is complete.”
“What the…” was all Dash said as the countdown fell from thee to zero.
“Initialization complete. Standby…”
Suddenly a pair of mechanical arms emerged from the sides of the armoire and clasped themselves around Dashes wrists, pulling her arms up over her head. Another pair emerged from the floor and clasped around her ankles, immobilizing her.
“Hey, what gives?”
The screen displayed a red highlight around her body and before she knew it smaller tendrils burst forth, stripping off her sports bra and shorts, undoing her ponytail and even untying her shoes, which she was lifted out of by the bigger arms before the smaller tendrils pulled off her socks.
“Sweet Celestia! Someone, help!” she screamed, but there was no stopping the machine. With its various maniples with scoured the room, fetching materials for its processes.
Dash’s nails were trimmed and painted with pink nail polish, and when she tried to protest the machine merely tightened its grip and shocked her until she learned to keep her mouth closed, at which point pink lipstick was roughly applied, pulling at her lips, then tidied up with a cloth.
Some of the more delicate maniples borrowed part of Rarity’s makeup kit, while another puffed a jet of air into her eyes one after the other, forcing them to close. She didn’t dare open them again as the machine began stroking her eyelids with a shader brush, pulling at the skin beneath her brow as it blended the pink eyeshadow.
Using a felt-tip, it applied coal-black eyeliner, the maniple working outwards from within until a clean accent was apparent at the base of the lashes.
Finally, using a fine-toothed mascara brush, the machine pulled upward against her eyelids until she opened, then applied dark mascara to her lids and lashes, shifting left and right as it tugged upward. This was immensely uncomfortable, yet the result might have been pleasing, if she had asked for it.
Next came the clothes.
A powder-pink crop-top with long sleeves was pulled down over her head faster than the eye could see. Apparently the machine didn’t plan on tailoring her a bra, so the bottoms of her breasts were still visible beneath.
Panties weren’t on the menu either as she was hastily equipped with a white, pleated skirt and matching belt patterned with Rarity’s signature diamonds in sky-blue.
She was at least given a pair of socks before the machine thrust a pair of white, high-heeled boots on her feet, zipping them up to the middle of her calves.
Golden bracelets, a silver pendant, and then an impromptu (and painful,) piercing of the ears that threatened to draw tears resulted in a pair of heart-shaped earrings.
After that a complex scene involving gruesome detangling, multiple curling irons and an almost lethal amount of hairspray transformed her mane into rainbow-ribbons, à la Rarity.
Then a dose of perfume knocked her out. When she awoke, she was strapped to Rarity’s bed, a monitor and an array of tendrils hanging over her.
The monitor would display a phrase and play recorded audio of Rarity reciting it, prompting Dash to then repeat the phrase. At first she didn’t understand, speaking it as she would without thinking. The monitor responded by flashing red and the assembled dendrites began to move. It was then that RD noticed they were carrying an assortment of ‘toys.’
As punishment, the mechanical arms raised her legs and spread them apart, then attempted to force a plug into Dash’s ass while she protested fearfully. Though a tight fit, the machine eventually succeeded.
Before the lessons were through she also had to master the art of flirtation and was tested through simulated interactions with boys from school.
By the time she was finished the machine had put painful clamps on her nipples and taped a vibrator to her clit. Then a ball-gag was placed in her mouth and a camera appeared before she was blindfolded and left alone for a time while the machine silently filmed her orgasms.
Next she was made to perform various gestures and hold uncomfortable poses that were either overtly sexual or just girly in the extreme.
The treadmill was, at least, a form of exercise. Walking in heels was difficult, but her balance was excellent, and soon enough she was tracing a thin line, one foot directly in front of the other, the sway of her hips coming naturally after that.
When Rarity finally returned she looked everywhere for Dash, saving the one room she hoped she had not entered for last.
“Machine! Administrator Override. Identification: Sparkler.”
The machine fell silent, still held Dash in place. Rarity looked her up and down, impressed with the total-conversion. Just how much of herself did she owe to this sadistic machine’s influence, she wondered?
Perhaps it was a little vain, but she thought Rainbow Dash looked good… really good.
“Wha- what are doing?” asked Dash, her voice cracking.
“Now now, is that how a lady proposes a question?” she said eerily.
She pressed herself up against her helpless friend, running her fingertips over every detail from the curly mane down to the skirt, and then…
“Ah!” sighed Dash, surprised.
“No panties? However did you get away with that?” teased Rarity.
Her touch was light, but somehow that made it more intense. Rarity unbuttoned her bellbottoms and started grinding on Dash’s thigh, and Dash had a sinking feeling that things would never be the same between the two of them again.
Author's Note
This was an interesting experience to write. The user who commissioned this was very specific about certain details, including the outfit, making sure that the makeover was described in detail, about the lessons and use of toys and even about Rarity having her way with Dash at the end. I hope I didn’t disappoint them too badly. 
Edit: I changed some things around last minute. Hopefully it feels more complete while still fitting in the 1k words bracket. 
