A Racisit Grandmother?

I swear, just about every time I go to my gramma's house, she pisses me off with racisit remarks.She's 86, and calls people "Those blacks" or "Those koreans" or "Those MEXICANS"-When she knows perfectly well i'm the only one in my family half mexican.I always clear my throat really loud when she says these things, and bite my hands so I don't go with my urge to say some,well,not nice things to her.My mom tells me to let it go.How,exactly?My best friends are black & vietnamese-Imoni,Steven & Ja'vonte-How do I let these remarks go?They hurt?