Upvote:1
Gauß was simply buried in the family grave of the Albani cemetery in Göttingen, next to his mother. So there she is/was, as almost all 'graves' on the cemetery were eventually destroyed, that of Gauß being of continued interest, and big to begin with, so still visible:
Trauerfeier in der Sternwarte und Begräbnis auf dem Albani-Friedhof in Göttingen (Familiengrab)
Axel Wittmann: Tabellarischer Lebenslauf von Carl Friedrich Gauß
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Die Stadt war ohne Zweifel der Mittelpunkt seines Lebens, hier wurden bis auf den ältesten Sohn alle seine Kinder geboren, hier musste er seine beiden Ehefrauen begraben, hier wirkte er als weltbekannter Wissen- schaftler, und hier fand er auf dem Albanifriedhof seine letzte Ruhe.
GAUSS ALS MENSCH – GAUSS IN GÖTTINGEN Göttingen zur Zeit von Carl Friedrich Gauß Ernst Böhme
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in
„Wie der Blitz einschlägt, hat sich das Räthsel gelöst“ Carl Friedrich Gauß in Göttingen
Göttingen 2005
Just to complement the question's confusion over the names to be found all around: the church register (Kirchenbuch) lists his father's name as Ge_b_hard Diterich (as he was called, but officially: Gerhard Dietrich), and his mother's maiden name as Benze_n_.
Upvote:3
The book you linked at archive.org, Gauss zum Gedächtniss by Wolfgang Sartorius von Waltershausen, from 1856, appears to say she was buried at the observatory in Gottingen. The relevant text (and translation via google translate) from the book:
The (approximate) translation (emphasis mine):
The daughter Dorothea, born in 1742, came to Brunswick around 1769 and married her there to Gauss' father in 1776. She was a woman of naturally clever mind, a simple, humoristic, cheerful mind and a firm character. Her great son was her only child, her stole! She clung to him with the greatest respect and love, as he clung to her with deep respect in her last hour. In good health, although blind from black cataracts in the last years of her life, she reached the unusual age of 97 years and died under the faithful care of our observatory, where she has been since, 22 years, on April 19, 1839.
(Note: The OP in comments says this interpretation is incorrect according to individuals on a German language forum.)
Another possible answer popped up in a much more modern work, though unsourced from what I could tell. A 2014 title, Creators of Mathematical and Computational Sciences, by Ravi P Agarwal, Syamal K Sen, mention the mothers burial in reference to that of Gauss himself (emphasis mine):
He was buried at St. Albans Cemetery in Göttingen next to the unmarked grave of his mother.