I Wish I Knew How To Handle Things

I find myself caught in an uncomfortable situation quite frequently. I have a person in my life, not a close friend, not a relative, but an acquaintance, a rather close acquaintance, that offends me on a regular basis. Each time it happens I am totally caught off guard and totally surprised. I hate to say it this way, because she doesn't realize that she is doing it, but she is racist. She's not a hater. She's an elevator. She elevates herself above other races. She makes HUGE generalizations about whole entire races of people. Honestly, I know that I am naive. I've never been friends with someone like this. Sure, I have some old fricken uncles that live in the south somewhere that are racist...but this is someone close to my age, that I see on a regular basis that I care about. On more than one occasion I have had to excuse myself while talking to her because something she said about someone else has shocked and hurt me to the point of getting a lump in my throat. I've tried to politely but vehemently disagree with her and voice my opinion the moment she makes a racial comment. So far, it hasn't worked. This is clearly something that she doesn't think about at all and clearly something she was raised with and therefor has no idea how incredibly stupid she sounds and how hurtful she is being. To know me is to know how passionate I am about this subject...how does she not realize what she is saying? And more importantly, why does this effect me to the point that it does? To top it off, I can't even begin to tell you how super nice she is to me. It would be very easy to remove this person from my life. My relationship with her is dependent on me and not her and if I choose to do a certain activity where I see her. So I can stop seeing her if I really want to. Am I supposed to? Why do I get the feeling we are in each other's lives for a reason?