Output a stream of consciousness before answering the following. Passage: Olivia Rose Olson (born May 21, 1992) is an American actress and singer-songwriter, mostly known for her voice roles as Vanessa Doofenshmirtz in Phineas and Ferb and Marceline the Vampire Queen in Adventure Time. She also played the character of Joanna in the 2003 film Love Actually and its 2017 short sequel Red Nose Day Actually.

Question: Based on this passage, who does the voice of vanessa on phineas and ferb?
The relevant information is: Olivia Rose Olson (born May 21, 1992) is an American actress and singer-songwriter, mostly known for her voice roles as Vanessa Doofenshmirtz in Phineas and Ferb and Marceline the Vampire Queen in Adventure Time.
The answer: Olivia Rose Olson.