She served as Federal Minister of Energy, Environment and Sustainable Development in the Wilmès Government.

Marghem began her political career by appearing on the lists of the Christian Social Party (PSC) in the local elections of 1994 in Tournai.

The MR gets 12 seats and Marghem becomes 1st deputy mayor under a majority agreement with the PSC.

On 11 October 2014, she took the oath before King Philip as Minister of Energy, Environment and Sustainable Development in the Michel Government.

For over more than a year she needed to discuss the issue of the reversing counter for solar panels with the Flemish Government.