Here is Sweetie Belle for my headcanon!

Bio:

Species: Changeling, Unicorn (Formerly)

Gender: Female

Friends: Apple Bloom, Scootaloo, Diamond Tiara, Silver Spoon, Babs Seed, Rumble, Fluttershy, Pinkie Pie, etc.

Enemies: Diamond Tiara (Formerly), Babs Seed (Formerly), Queen Chrysalis (Formerly), Tirek, Prince Blueblood, etc.

Family: Cookie Crumbles (Mother), Hondo Flanks (Father), Fleur-De-Lis (Aunt), Fancy Pants (Uncle-in-law), Rarity (Big sister), Spike (Brother-in-law), Twilight Sparkle (Adoptive sister-in-law), Queen Chrysalis (Adoptive brother-in-law), (Adoptive sister-in-law), Queen Chrysalis (Adoptive sister-in-law), Nyx (Adoptive cousin), Twila (Adoptive cousin), Larva (Adoptive cousin), Crystal (Adoptive cousin), Twilight Velvet and Night Light (Adoptive parents-in-law), Shining Armor (Adoptive brother-in-law), Cadance (Adoptive sister-in-law), Skyla (Adoptive cousin), Flurry Heart (Adoptive cousin) and Pipsqueak (Coltfriend).

Note: Sweetie Belle becomes a metamorphosed changeling when the Changeling Hive is need of volunteers to help protect the changelings from danger.

Note II: Sweetie Belle is pink (A fated pink) in my headcanon just like her mother Cookie Crumbles.

Note III: The events of Season 8-9 (With the exception The Washouts and Best Gift Ever) are not canon to my headcanon.