How is St. Maria Goretti a martyr?

St. Maria Goretti was stabbed several times for her refusal to consent to sin against purity; Alessandro Serenelli, her "would-be rapist" (ch. 25 of *Modern Saints: Their Lives and Faces* vol. 1 ), was trying to seduce her. Certainly it is heroic that she would rather die than to consent to sin, but how is she a martyr? I thought martyrs had to die *in odium fidei* (because of hatred of the Faith).