Tellegen was a former top official of the town Utrecht, which dismissed herself when a NSB Mayor was appointed. She became part of the resistance and was known as 'Dokter Max'. She lived on Maliebaan 72bis and was the neighbour of the Sicherheitspolizei. She organised the financial support of thousands of railway strikers in the autumn of 1944. After the war she became the director of the office of the Queen.