Buttercup Cottonwood was born and raised in Maretropolis, but frequently visits her extended family in the country. In addition to being strong and agile, Buttercup is also brilliant at solving mysteries. Her skills earned her her cutie mark as a filly, and her income as an adult.
One fateful day, however, her father was assassinated. Now working to solve the mystery of his killer's identity, Buttercup took up crime-fighting to ensure that no one else would suffer loss as she had. She works alone, and emotionally distances herself from others because she's afraid she'll lose them too.
Design changes: First off, she's half-horse this time, and has a lighter patch on her face. I also changed the hue values of her coat and eyes just a little bit towards yellow-green. I set her ponytail (pun not intended) a bit lower as well.
Backstory changes: Her backstory remains more or less the same, minus the "Improbable Age" trope. I also removed Autumn, the killer from the previous version, from the picture. She just wasn't quite believable as a character, and revealing right off the bat who the killer was kind of ruined any potential for mystery. I might recycle her in a different role, though. Who knows.