Mannheims is one of the few lawyers in the Netherlands who specialise in air traffic law. Moreover, she specialises in international criminal law. Her clients are individuals, (foreign) companies and authorities. From 2001 to October 2009, she was portfolio holder for criminal law in the Supervisory Council of the Amsterdam Bar Association. Additionally she was acting Dean for four years. Since November 2009 she has been a member of the board of the Dutch Association of Defence Council. Furthermore, she is a lecturer in law of criminal procedure at the OSR and at the Law Firm School, and frequently lectures as a speaker at seminars.
Mannheims is recommended by the Legal 500.