Marry is involved in public-private regulatory matters, and specialises in public economic law and corporate governance. She is a trusted boardroom adviser. Marry's expertise ranges from research issues, advising on the effects of proposed legislation, regulatory aspects related to the regulatory authorities, the enforcement of existing laws, and conducting various proceedings. An example of her expertise is the leading role she played in the widely discussed liquidation of Vestia's €20 billion derivative portfolio.
Marry combines her legal work with non-executive director roles, including as a supervisory director for De Nederlandsche Bank and KLM. She is also the chair of the theatre production company Internationaal Theater Amsterdam. Marry has previously served as a supervisory director for Royal Haskoning DHV, GVB Amsterdam and the health insurer VGZ. In addition, she lectures on boardroom dynamics at the Governance University and organises Round Table meetings for supervisory directors, during which matters such as governance issues are addressed. Furthermore, Marry is a business partner (co-host) in BNR Nieuwsradio's 'Zakendoen'.