She and Mimi were best friends as little kids, but they grew apart as they got older and by the start of the series, are rivals/enemies. Sincerity's current best friend is a girl named Hayley Kinaschuk.
Sincerity has pink short hair with messy bangs and two loops hanging out from the sides of her head that are held by a green clip. She wears a yellow shirt and an orange wool tank top over that. She wears orange leggings and green platform shoes. She has blue eyes.
Despite her name and beauty, Sincerity is a spoiled, selfish rich girl that wants everything to be done her way whenever she wants it.