I understand to some extent how you feel. I grew up in the MS Delta and finally left to join the Navy and see the world. Years later, when I brought my Asian wife home to meet them, my mother pulled me off to one side (before we ever got inside the house) and said, “I wish you’d just married a Black girl instead”.
Thing is, I understood that she was trying to be polite by not using the N-word…because she really didn’t like Blacks (as was the case with my whole family there). She just said that because she liked Asians even less than she did Blacks, probably because she was so unfamiliar with their culture.
Time passed and all my close family there has passed away. My grandchildren won’t look White at all…which is precisely what my mother (and my much-more racist grandmother) feared, but I’m quite happy with it.
As you said, your grandmother doesn’t define you. Just hope that someday they’ll see the light and change. My mother did to some extent, though my grandmother never did.