SEGA Asia recently revealed Erina's character profile for Persona 5 Tactica. Check it out:
A girl who comes to the rescue when the gang stumbles into a strange new realm.
Erina is the beloved leader of the Rebel Corps, having earned the adulation of her troops through her drive and energetic personality.
In order to carry out her revolution, she proposes a deal with the Phantom Thieves.
Source: YouTube