Rainbow Pie
The idea of soulmates is as old as time itself. The first appearance of them had been dated all the way back to Starswirl The Bearded's era, just before the Pony of Shadows incident, when two ponies had felt a weird, magic-like sensation and pulled them closer together. Not in a literal sense, but more like astrophysical. It had been said that the pull felt more like a calling than anything. Pretty soon, the feeling began to pop up more often than not, and it continued long before it was finally given a name, a year later after Starswirl had disappeared.
Soulmate.
Soulmate magic didn't work the same way regular magic would; it was unpredictable, often without warning, and nine times out of ten, most ponies were more lucky than not. Sometimes, you can get the wrong soulmate, and other times, not at all. Ponies who were studying this have long since given up on making an accurate study of soulmate magic. At best, it's usually the strongest when mutual feelings are at play. At worst, it could tear what could've been normal friendship apart. There was no indication of long-term symptoms of soulmate magic, other than a broken heart. Those who were affected by soulmate magic, and have recently fallen out of with their supposed partner, showed no difference than those who were sad or disappointed.
All of this would've been good to know (well, if she had actually paid attention as Twilight often scowl at her for) when Rainbow Dash had felt the soulmate magic.
It wasn't like she didn't believe it exist, unicorn magic exist after all, but Rainbow Dash had...never seen herself as the type to be tied down before. She knows she's too much, that she's often selfish, and never thought about the consequences of her actions. She understands her brash personality, borderline tomboy, could put some ponies off. She's been told she doesn't think when she speaks, due to her saying things at the wrong time, and could be self-absorb when she wanted to. She knew all of this, and though it'd hurt, Rainbow wouldn't change herself for the world. She loved herself, she thought she was awesome, and if she had to lessen herself all because whoever she gets attracted to due to this soulmate magic thing didn't like it, it would hurt her in the long run. She was the way she is because her parents taught her how to be confident, even when she wasn't at her best. It took a while to understand it, but when she did, Rainbow tried not to doubt herself again. Not only for herself, but also because she had a reputation to uphold.
So no. She didn't want a soulmate, or soulmate magic to ruin what she had built for herself. She'll run (fly, whatever) as fast as she could to get away from it.
The few times she had felt the soulmate magic, she ran. She knew one of the many soulmates, or those who are willing to be her soulmate, had been Gilda. The two had shared a lot in common, so she could see why Gilda had wanted something more from her, but Rainbow had only saw her as a friend. Plus, Gilda probably liked the idea of soulmates as much as she did - which is not at all, at the time. She could see why the two could've been together, if Rainbow Dash hadn't been trying to escape that fate.
The ice breaker, though, was when Gilda had revealed her true colors, and yelled at Pinkie. The way she had talked down to everyone, especially Pinkie, had set Rainbow Dash's soul on fire and of course stood up for her. Especially since she was the one who had done all those pranks to begin with. And as she had stated to Gilda, it was sheer dumb luck (or because of bruise ego) that she was the one who set them off. Nobody had told her to act so rudely and outshine everyone. After that, soulmate or not, Rainbow Dash decided that a relationship with Gilda was not the best for her, and whatever magic that could've happened between the two, frizzled out.
Another pull of soulmate magic that came to mind had been Rarity. This one had been odd because as far she knows, her and Rarity were complete opposites - not as bad as AppleJack and Rarity, however. Rarity liked all that fancy-dancy, uptight parties and stuff and Rainbow Dash...just wanted to chill. And have fun. She couldn't see how they would ever get together due to the clash of personalities and how they go about anything. The soulmate magic had frizzled out too, due to Rarity's conflicting interest in AppleJack and Fluttershy. They still remained friends, though.
AppleJack had been another would-be relationship due to soulmate magic, due to how stubborn they both were. It was fun, getting a challenge every then and there, and Rainbow Dash liked being around AJ. She wasn't too erratic like Pinkie (hahaha, oh how the fates turned on this), nor was she too uptight and proper like Rarity or Twilight. When it comes down to it, AppleJack was the shoulder you can lean on, and never had to say a word.
The problem, however, comes from the fact that, like Rainbow Dash, AppleJack doesn't know when to think before opening her mouth. The difference, though, is that AppleJack is honest to a fault. The very problem Rarity had when she had asked AppleJack to give her opinion on her fashion show. It's not like AJ is going to lie, not after that one time, but sometimes honesty can be brutal and not everyone has thick skin (see: Fluttershy). On top of being too honest, AppleJack is also very, very set in her ways. Maybe it's because that's how she's been raised, but AJ can be...very out of touch, with the local trends and such. Rainbow probably blames it on being raised, if she had to be honest.
That relationship can be very rocky indeed, due to how AppleJack views hard work and Rainbow Dash's sometimes lazy personality. Thankfully, Rainbow was spared when the pull towards AppleJack stopped when the blond earth pony had set her sights on Twilight.
But the next pull...oh my god, the next pull.
Pinkie Pie. A.K.A the pony that makes the best parties, often loud and cheerful, never had anything negative to say about anyone, always knew how to cheer them up, and just so...so...crazy.
Rainbow loved it.
Oh no.
The fact of the matter is, Pinkie Pie completed her in a way no one's ever did before. She was always Rainbow Dash's number one cheerleader, knew how to have a good time, and mind her personality too much. She was the one that just constantly stuck by her side, going through extreme lengths to do so, and while often annoyed with her antics, Rainbow Dash really didn't mind. She knows Pinkie Pie was a good soul, through and through, and she knows she only has good intentions. Every time Pinkie had gotten sad or mad due to Rainbow Dash's own negligence, Rainbow had wanted to tear her mane apart because Pinkie wasn't suppose to be sad. The way Pinkie just...deflates whenever something awful happened was enough to tear at the Pegasus' heart, because gosh darn it, it's Pinkie Pie. How can someone who could literally be born out of the sun itself be sad? And why is it so heartbreaking when she is?
Maybe because it's expected of her, Rainbow thought bitterly. They all knew Pinkie Pie as the pony who loves to see others smile, and nobody ever questions it, but...if Pinkie was really, really, really sad, who does she turn to? Rainbow had never heard from Mr. and Mrs. Cake about Pinkie being sad, or just in general upset. They mention it once in a hearing, but by then, everyone knew Pinkie was upset. She had been out and about with them whenever an incident occurs and she left to go to her room in Sugar Cubes. Rainbow doesn't count those times.
And maybe this was the reason Rainbow decided to stop running from the pull of soulmates. Because out of everyone she could've been with, maybe it was Pinkie Pie who deserve it the most. She was the laughter of their group, but even laughter needed a break every now and then. And it doesn't help that Rainbow Dash does find Pinkie appealing, especially since Pinkie has does nothing, but cheer Rainbow Dash on, believing in her twice as much as Rainbow Dash usually believes in herself.
"Hey, Dash?" She heard Pinkie's voice. "Have you seen where Gummy went?"
Rainbow Dash stretched herself around her cloud, yawning. "Not really. He's missing?"
"Yeah, I'm getting worried. Gummy usually never leaves on his own." Rainbow can hear the concern in her voice and she nuzzled the pink pony, who giggled.
"I'll tell the others and we'll search together, okay? He couldn't have gone that far." She said, getting up and stretching her wings.
"Okay, I'll check Sugar Cubes again. Thanks Dashie, love you!" There was kiss placed on her head and Rainbow Dash smiled.
Yep, she was glad she stopped running from the soulmate magic. And she was specially happy that it was because of one, pink, Earth pony.