Born in Egypt, Tilley was educated in Kent and has lived in Cornwall since 1978. She is a watercolourist whose subject matter includes landscape and the human figure. A member of STISA since 1999 (and chair from 2003 to 2009) she has exhibited widely throughout Cornwall, participating also in shows further afield in Plymouth, Exeter and London. Her work is held in the National Trust collection (Godolphin Estate), the Chris Beetles Gallery in St James, London, as well as private collections within the UK, in Europe, the USA and Japan. In 2002 the critic Frank Ruhrmund described her as a 'recognised exponent and authority on watercolour painting'.

The artist is well known as a tutor and demonstrator for art societies in the south west of England. Based in Hayle, she works closely with the National Trust at Godolphin House within the educational and arts activities programme.