O'Connell grew up in Taunton to divorced parents who ended up on housing assistance to meet family expenses.

O'Connell launched her first state representative campaign against incumbent Democratic state representative James Fagan in June 2009,[3] citing comments Fagan made in 2008 during a debate on a child sexual assault bill[4] as her inspiration to run.

[8] She faced controversy at the start of her mayoral campaign,[9] with CommonWealth Magazine reporting that Massachusetts Lieutenant Governor Karyn Polito had given O'Connell notice that incumbent Taunton Mayor Thomas Hoye would not run for re-election.

[11] In June 2023, their younger daughter went missing from an addiction and mental health treatment center in Hilliard, Ohio.

[12] On July 22, 2024, O'Connell was arraigned on charges of assault and battery on a household member and assault and battery with a dangerous weapon after she allegedly bit and struck her husband with a crowbar during an argument at their home on July 19.