Talie was one of Ashley's friends and party members in the dungeon.
She was captured and made into a breeding slave, leaving her hollow and mindless on the twenty-first floor of the dungeon.
There's a scene related to finding her, requiring Julia to be in the party. If Julia (Normal form) is alone with you in the party, or if you also brought Ashley (Normal or Berserker form), it unlocks Ashley's Berserk spell.