In 1996, she earned a bachelor's degree in international relations from James Madison College at Michigan State University.

She then worked as a real estate agent at RE/MAX Advantage and served on the City Council of Portage, Michigan from 2003 to 2010.

O'Brien was first elected to the Michigan House in 2010 and became active on private property rights, education reform,[2] adoption, and direct access to physical therapy.

She worked on bills to ensure the rights of people with service animals,[4] to provide state IDs to the homeless, to protect victims of domestic violence,[5] to enact safe passing distances for vulnerable roadway users,[6] and to train caregivers of seniors and people with disabilities.

[7] O'Brien is known for her work to change Michigan's sexual assault laws in the aftermath of the Larry Nassar scandal, alongside advocates including Rachael Denhollander, Aly Raisman, Amanda Thomashow, Sterling Reithman, and Larissa Boyce.