Here's why:
* The Room of Requirement only appears for the characters the game focuses on. You can't interact with or control Hanna Abbott, nor can you influence who appears in the Room.
* The Room's purpose is based on the player's needs. It adapts to what the player needs at that moment, like a specific potion ingredient or a training area.
While you can't have Hanna Abbott in the Room of Requirement, she does appear in the game at Hogwarts, allowing you to interact with her.
Is there anything else you'd like to know about the game or Hanna Abbott?