Mairin obtained a first degree in German, Italian and European Studies at the University of Bath. She is a qualified Modern Foreign Languages teacher, having completed a PGCE at the University of Oxford, and has taught in a variety of cultural and institutional contexts.

Mairin continued her postgraduate studies at the University of Oxford focusing on areas of Applied Linguistics and SLA. She obtained an MSc in Applied Linguistics and Second Language Acquisition and then an MSc in Educational Research Methodology. Under the supervsision of Professor Macaro, she completed an ESRC funded doctoral study investigating the relationship between formal Modern Language instruction and the development of active European citizenship. Mairin's DPhil also examined adolescents' attitudes and motivations for language learning. Since then her work has primarily focused on the two key areas of language learning motivation and the relationship between language learning and citizenship, exploring both aspects of the student learning experience and the professional development of language teachers.

Mairin has worked at the University of Oxford, Newcastle University and at the University of Edinburgh. She has researched and published in the fields of SLA, Applied Linguistics and Language Education.She works closely with schools, delivering professional development for language teachers and has also been invited to deliver a range of research and teaching sessions at universities across Mainland China and parts of Europe.

Mairin is Associate Editor for the journal System and a co-Editor of the Edinburgh University Press Applied Linguistics Series. She is a Fellow of the Higher Education Academy of the UK, a key member of the HKU Consortium for Research on Language Policy and Practice and a member SIG Intercultural Communication of the British Association of Applied Linguistics.