Gretha was born in Enschede, The Netherlands in 1984. She was taught by Hannie Kruijt.
She studied bassoon at the Royal Conservatoire in The Hague with Johan Steinmann, Prof Gustavo Núñez and Dorian Cooke.
She continued her studies at the Musikhochschule in Mannheim with Prof Ole Kristian T Dahl.
As a freelancer she has worked in different European countries with orchestras and ensembles such as the Rundfunk Sinfonie Orchester Berlin, Rotterdam Philharmonic Orchestra, Radio Philharmonic Orchestra (NL), Bergen Philharmonic Orchestra, Norwegian Radio Orchestra, Opera de Rouen, Asko-Schönberg Ensemble and Netherlands Wind Ensemble.
She has won several prizes and competitions, for example the Prinses Christina Concours (NL), Young Music Talent of the Year (NL) and the German Musikhochschule Competition.
In 2006 she substituted for principal bassoon in the Norrköpings Symphony Orchestra (Sweden) for half a year. In 2010 she became principal bassoon of the City of Birmingham Symphony Orchestra and since 2014 she has been principal bassoon of the Hallé Orchestra. She also plays with the Birmingham Contemporary Music Group and has done guest work in the LSO, LPO and The Academy of St Martins in the Field.