See, I think that's very big of your g-ma. I don't know if I could say the same about myself if I'd grown up in those times. Very doubtful, in fact. Taking the higher road and turning the other cheek all the time are emotionally exhausting. But, you can either live a life steeped in hatred or you can try to rise above it. I'm glad your g-ma was able to rise above.
My theory on "prejudice" is that the ability to recognize and associate physical characteristics with similar or repeated behavior patterns or any other similarities between or among people, places or things in the wild is an innate and crucial survival mechanism. It's how we "learn" and survive. But, our big, advanced human brains allegedly further allow us to make further distinctions and more finely tune this ability. I feel comfortable saying that every red-hot, glowing stove burner is going to burn me. But, I don't think that every blonde-haired, blue-eyed, pale-skinned person wants to see me dead simply because of my ethnic makeup, unless they specifically indicate otherwise, even though there are actually some who do.