Manthe was born and raised in St. Clair Shores, Michigan. She graduated from St. Clair Shores High School and went on to earn a bachelor's degree in business administration from Michigan State University. After college, Manthe worked in the private sector before starting her own business, a marketing and consulting firm.
Manthe became involved in politics in 2016, when she was elected as a delegate to the Republican National Convention. She also served on the St. Clair Shores City Council from 2017 to 2018.
In 2018, Manthe was elected to the Michigan House of Representatives for the 38th district. She defeated Democratic incumbent Sarah Roberts by a margin of 2,491 votes (51.3% to 48.7%).
As a member of the House of Representatives, Manthe has served on the Appropriations, Transportation, and Judiciary Committees. She is also a member of the Republican Leadership Team.
Manthe is married to her husband, Scott, and they have two children. They reside in St. Clair Shores.