Sargent describes herself as "born, raised, and educated in Madison". She graduated from Madison East High School and the University of Wisconsin-Madison. In 2010, Sargent's neighbors on the north side of Madison urged her to seek the 18th District seat on the Dane County board of supervisors upon the retirement of the incumbent. "At that point, I owned my own business," she said. "I had three kids, and I just found out I was pregnant with my fourth. And I was 40 years old and feeling like one more thing on my plate would cause me to topple over." But then her children came home from school complaining about having to do a community service project, and she told them to tough it out. Then Sargent, says, she decided she needed to do the same. Sargent won her race, and has been part of the liberal majority on that body, chairing the Health and Human Needs Committee. On January 23, 2014, Melissa proposed Bill LRB 3671, which would legalize marijuana for recreational and medicinal purposes in Wisconsin.
For fifty consecutive days during the 2011 Wisconsin protests against Governor Scott Walker's controversial "Budget Repair" legislation which abolished collective bargaining for most Wisconsin public employees, Sargent says that she, often accompanied by one or more of her four children, joined in the mass demonstrations, whether in the Wisconsin State Capitol or, outside in the Wisconsin cold. On March 27, 2011, when the State Capitol Police ordered her three older boys to take down their protest sign proclaiming "Solidarity Forever" which was being displayed outside of the "Designated Demonstration Area" they refused, and Sargent was issued a ticket.
Running for the Assembly
After the State Assembly was drastically redistricted in 2011 by a Republican-controlled legislature, former 48th district incumbent Democrat Chris Taylor had chosen to run in the newly-revamped 76th district. Sargent was unopposed in the Democratic primary election. In the general election she polled 24,375 votes, to 4849 for Libertarian Terry R. Gray and 62 scattered votes.
Personal life
Sargent owns a company that makes giclée prints of original artwork. She has four sons.