She doesn't actually go by swirlpaw anymore because she can't remember that's her name
Uh essentially she was a BranchClan apprentice who got lost in the mist(probably ran away because her seeing ghosts freaked cats out) and instead of disappearing/losing her memories she just lost her memories and stayed in the mist and became slightly psychopathic because she's a little messed up. Sooo she just kind of made a bunch of ghost friends who she doesn't remember but they just do mean stuff together and it's fun