headcanon: she has DID, ae-cha is the kind side of her while angela is the one who has all of the negativity due to the trauma she went through as a child.
explanation: ae-cha is called angela by everyone else since no one knows that angela has DID, and angela hates being called ae-cha so they are both called angela until lars decided to call ae-cha "angie" and to everyone's surprise, angela didn't flip out, so it sticked to ae-cha as a nickname that can belong to her.
