Van den Brandeler, descendant of the noble Van den Brandeler family, was a daughter of engineer Jhr. ir. Willem Cornelis Quirin van den Brandeler (1885-1971) and Hillegonda Baroness van Randwijck (1888-1970), 
descendant of the Van Randwijck family , and granddaughter of mayor Frans Willem baron van Randwijck, lord of Rossum and Heesselt (1854-1930), about which place she first published memories; she was named after her maternal grandmother, Jkvr Agnes Boreel (1853-1916), descendant of the Boreel family. She married her relative Jhr. ir. Andries Louis van den Brandeler (1918-1991) in 1963, from which marriage no children were born.

Van den Brandeler studied at the Vrije Studio (The Hague), the Royal Academy of Art (The Hague), the École des Beaux Arts (Paris) and the Escuela de Artes Graficas Barcelona. 
She was a student of Han van Dam, Demetrios Galanis, Henk Meijer and Willem Rozendaal. She worked in The Hague, Barcelona, Madrid, Greece and the place where she would also die. She painted portraits, still lifes, but also other genres. She was also an illustrator, especially of work by Leonard Roggeveen, 
and a book cover designer. She was a member of Pulchri Studio (The Hague), co-founder and secretary of the Haagse Aquarellisten, a member of the Dutch Circle of Drawing Artists (with which she exhibited in 1964 at the Stedelijk Museum Amsterdam) and of the Community Visual Artists.