In all of the things I've read about Edith Stein, I don't think I've ever seen a reference to her as a "martyr" -- at least in the formal sense from the perspective of the Catholic Church.
What is the basis of her beatification?
Maximilian Kolbe was one such person -- he was one of the first saints canonized by Pope John Paul II in the late 1970s.
And many more, some of whom were recognized and many more who were not.
A "martyr" in a formal Christian sense is one who gives up his or her life for her faith in Christ. Edith Stein was canonized in recognition of her life of spiritual devotion as a Carmelite sister.
And many more, some of whom were recognized and many more who were not.
You really have to understand the canonization process -- it is distinctly not a "political" process, though politics will often come into play as far as the timing of someone's canonization is concerned. Pope Pius IX, for example, was only recently canonized even though later popes such as Pius X and Pius XII had already been canonized. This delay was the result of the Vatican's desire to avoid having the canonization process influenced one way or another by Italian political sentiment related to the issues surrounding the unification of Italy at the time Pius IX served as pope.