Como o Hagrid, ela tem sangue gigante.
Da entrada de Pottermore para a "Academia de Magia de Beauxbatons":
Headmistress Olympe Maxime is (in spite of her protestations to the contrary) half-giantess; brilliant, elegant and undeniably awe-inspiring.
Alternativamente, esta questão foi sugerida de forma indireta em uma entrevista Relíquias da Morte
:Did Hagrid ever get married and have children?
No. […] No, no, Hagrid never did marry and have children. […] Realistically, Hagrid’s pool of potential girlfriends is extremely limited. Because with the giants killing each other off, the number of giantesses around is infinitesimal and he met one of the only ones, and I’m afraid, she thought he was kind of cute, but she was a little more, how should I put it, sophisticated than Hagrid.
Esta passagem deve estar se referindo a Madame Maxime, e assim deduzimos que ela é giganta (embora ao contrário de Pottermore, isso não confirma que ela é metade -gigiosa)