In October 2001, she joined the S4C live teen magazine programme Uned 5 (Unit 5) as a presenter.
Between April 2008[2] and December 2009, Gwilym presented S4C's now-defunct flagship arts programme, Sioe Gelf, and its replacement, Pethe.
In summer 2003, Gwilym joined BBC Radio Cymru to present a twice-weekly late night show for the station's C2 youth strand - broadcast live from BBC Cymru's studios in Bangor and including contemporary Welsh language music, features, news & interviews and listeners' texts & e-mails.
She went onto present early morning and weekend afternoon shows, and in November 2010, C2's flagship 8-10pm slot each weeknight.
From February 2018 to July 2021, Gwilym also presented a Sunday morning breakfast show for BBC Radio Cymru 2.
[8] Originally from Henllan in Denbighshire, Gwilym attended the village school and Ysgol Glan Clwyd in St Asaph,[9] before studying psychology at Cardiff University.