Coco Swirl who lived in the Canterlot wanted to live in Ponyville so she won't be treated like royality like she is. After some time of living she met these sweet mares, but one in particular will change her life
It seemed like an average task: My faithful student, Twilight. I ask that you please come to Canterlot immediately. I have an important task for you to take. This task will help us get a better understanding of species other than pony kind. Your teacher, Princess Celestia. Little did I know, it would lead to one of the most long-lasting and meaningful relationships of my life.*
*Credit goes to UnleashedTwilight on FimFiction