She was awarded the BBC London Theatre Award for outstanding performance in a musical in 2001 for her role in the National Youth Music Theatre's production of The Dreaming.
She graduated in Drama from the University of Hull and trained at the Royal Welsh College of Music & Drama.
In 2005, Sian's brother Llŷr had an epileptic fit and was discovered he had an inoperable brain tumour. In June 2018, the tumour became high-grade, and Sian decided to run the London Marathon in 2019 for The Brain Tumour Charity. Llŷr passed away in February 2019