Since 2008, she has conducted extensive research on career guidance in Norwegian schools, collaborating with practitioners, schools, policymakers, and public authorities. Her research explores how career guidance professionals navigate complex and sometimes conflicting expectations shaped by policy frameworks, organisational conditions, local communities, and the needs of guidance seekers.

Drawing on sociology, street-level bureaucracy, recognition theory, and improvisation studies, Mathiesen has developed the concepts of contextual, political, and relational balance, improvisational career guidance, Mission Musicality, and the improvisational ethos. Her research has contributed to national and Nordic discussions on quality development, professionalisation, equity, and policy development in career guidance.

She completed her PhD at the University of Stavanger in 2022 with the dissertation Balansekunst: Skolens rådgivning i møter mellom kontekstuelle, relasjonelle og politiske forventninger [The Art of Balance: Career Guidance in Meetings with Contextual, Relational and Political Expectations]. Her publications include research on improvisation in career guidance encounters, policy enactment, professional discretion, and inequalities in education and career choices.

At the heart of her work is a concern for how professionals can create meaningful encounters with people in situations marked by uncertainty, vulnerability, and competing expectations.