I think it’s important to understand what it means to make a person a saint. That simply means that we are certain that this particular person is in heaven. All people in heaven are saints.
So, canonizing Edith Stein is an acknowledgement that she is in heaven. I’m aware of at least one miracle attributed to her intercession which was part of the evidence of her cause for sainthood. Whether or not the martyrdom status is accurate or not since she died for being Jewish is an interesting side issue, but it shouldn’t negate the recognition by the Church that she is in heaven now.
Here is a short article about the family of Edith Stein who were at the Vatican for her Canonization:
depts.washington.edu/uweek/archives/1998.11.NOV_19/_article4.html