As I said, she's versatile.
She's Derpy Hooves when she's derpin'
She's Fluttershy when she's being pacific and nice and sweet
She's Rainbow dash when she's kicking Assholetep's ass and going all Kamen Rider
She's Rarity when she's tidying up her tomb world and picking a fancy pair of royal pauldrons to go to a cocktail party
She's Applejack when she's having none of the other grimdark characters' bullshit
She's Pinkie Pie when she's breaking the 4th wall and being quirky.
Blue is just Applejack. Kinda.