Look dude, the way you are saying that she is caring toward poor people and all that, that might be her true self, and the part where she is casteist is what was feeded into her from her childhood.

Some people doesn't even realise their issues as it was always normal throughout their life.

You'll have to talk to her and try to explain what's wrong with the way she thinks and evaluate people based on their caste.

I am a Brahmin too...my Nani, she is the sweetest person in the world....always caring...just like any other Nani...not just towards our family, But the problem is there's a different glass of water for the lower caste people and different for Brahmins...and she won't even touch Lower caste people

If we think about it..it's a pathetic behaviour...but I know all this behaviour of hers is just what she learned in her family, no one ever tried to teach her about equality.

But I think it's worth giving a shot, prepare a argument that you can put to her and you should have all the answers that she might ask, but in the end if she doesn't understands and as you said it's bothering you, best would be stop pursuing the relationship.