Monica was born in March 1969 to an Irish family, and she has a sister named Gabrielle. She pursued her passion for drama at the Guildhall School in London, graduating in 1991. Following her graduation, Monica embarked on a television career, showcasing her remarkable versatility as a character actress. Her performances often delve into the darker aspects of life, with notable roles including Maria Marchese, a real-life stalker, in the 2009 television film U Be Dead.
She also portrayed Miss Gilchrist, a demure yet deadly character, in the 2006 adaptation of Agatha Christie's Poirot novel After the Funeral. Monica's most notable role to date is arguably her portrayal of serial killer Rosemary West in the 2011 television film Appropriate Adult. Her performance earned her a BAFTA award, alongside her co-star Dominic West, who also graduated from the Guildhall School.
In a surprising twist, Monica was not the killer in the 2009 episode of the popular television series Midsomer Murders, titled The Great and the Good. However, she made up for it by playing twin sisters in the 2013 episode of Call the Midwife, with one sister being kind and the other less so.
On stage, Monica has continued to showcase her villainous side in various productions. She played Regan in a production of King Lear alongside Ian McKellen and took on the role of Lady Macbeth in an unconventional adaptation of Macbeth set in Africa, where she was the only white protagonist.
In 2014, Monica appeared in the television sitcom W1A, playing a lighter role. However, she was back to her enjoyably horrid ways as George Mackay's bigoted mother in the film Pride, released the same year.
