Police officers shielded Ursula Haverbeck from physical harassment, and she eventually left the site in a car, DPA reported without giving further details.
Haverbeck is a notorious extremist who was once chairwoman of a far-right training centre shut down in 2008 for spreading Nazi propaganda.
She was sentenced in November to 10 months in jail for Holocaust denial after a trial in which she insisted that Auschwitz was "not historically proven" to be a death camp.
That is "only a belief," said Haverbeck, dubbed Nazi-Oma (Nazi grandma) by the media.
She had also gone on television to declare that "the Holocaust is the biggest and most sustained lie in history".
On Thursday, she sought to attend the opening session of a trial against Reinhold Hanning, a former guard at Auschwitz who was charged with at least 170,000 counts of accessory to murder.
Some 1.1 million people, most of them European Jews, perished between 1940 and 1945 in the Auschwitz-Birkenau camp before it was liberated by Soviet forces.