Her professional name is a tribute to her late father Brian. She chose the name while at drama school, to avoid confusion with fellow Irish actress Aisling O'Sullivan.
In 2014 she won a British Comedy Award for Best Female TV Comic.
In 2012 she won Foster's "So You Think You're Funny?" at the Edinburgh Fringe festival.
On the 3 June, 2024, she announced that she was expecting her first child.