In 2018, she ran for Wisconsin State Assembly to replace Adam Jarchow, who was not seeking another term.[2] She was unopposed in the primary election and went on to defeat her Democratic opponent in the general election, carrying 59% of the votes.[3]
In 2020, Magnafici was re-elected to a second term, defeating Democrat Kim Butler in a rematch of the 2018 election.[4]
In 2021, Magnafici proposed legislation to prevent the University of Wisconsin System and Wisconsin Technical College System from requiring on-campus students to be vaccinated or regularly tested against COVID-19 in order to access campus buildings.[5]
On January 5, 2021, Magnafici was one of 15 Wisconsin state legislators, all Republican, who signed on to a letter asking then Vice President Mike Pence to delay the counting of electoral votes on January 6.[6]
In 2022, Magnafici was re-elected to a third term, defeating former Democratic state senator Patty Schachtner.
In 2024, Magnafici was moved into the 75th district as a product of redistricting, and declined to seek re-election. In the primary she endorsed Duke Tucker, who went on to defeat two other Republican opponents and defeated Democrat Jane Kleiss in the general election.[7][8][9]