My best friend always says things that curse me.

She's not cursing you, it's just her habit. Generally, if you carefully observe such a person, you will find that no matter who he talks to, he has this problem. Don't take it too personally. If he is really upset, you should bring it up to his face, but the tone should be like a joke, otherwise it will be counterproductive. If it still doesn't work and you're not happy, then learn from him and let him have a taste.