Koster was a coordinator of teaching methods of several varieties of Drèents and helped compile a Drèents spelling and literature course for local radio station Radio Noord.
RTV | RTV Pink | Noord | Rotterdam-Noord | RTV Slovenia Big Band | RTV Noord |
Later she worked for RTV Noord-Holland, Amsterdam FM, SBS Hart van Nederland and since 2007 for commercial newsstation BNR Nieuwsradio.