When she was four years old, Sir Reginald came to believe that Vanya's power was too destructive and dangerous. He put her on medication to suppress her emotions (as her power is tied to her feelings) and also had Allison make Vanya believe she was "ordinary".
This caused Vanya to feel extremely isolated and insecure. As an adult, she wrote a book about her famous family, alienating her from them further.
During Season 1, she befriends a man named Leonard Peabody – real name Harold Jenkins – who discovers the truth about Vanya's power and pushes her to unlock it in a bid to bring down the Umbrella Academy (he'd been obsessed with them growing up as he was born on the same day as them – only he didn't have powers).
After injuring Allison, Vanya discovers that Leonard has been using Sir Reginald's journal to manipulate her, and she kills him. She seeks refuge with her family, but Luther knocks her out and locks her in a soundproof chamber, believing her to be dangerous. Feeling alone and betrayed once again, Vanya cracks, using her heartbeat to harness enough energy to escape the chamber.