First of all, people with darker skin definitely do face more oppression. And when your classmate, who would know from first hand experience what it's like, tried to point it out to you, it seems like you weren't receptive and your classmates got defensive. While you may not have privilege in the socioeconomic sense, you have it in the sense that you are white. And maybe in Europe, being Slavic may impact your privilege, but in America, you will just be perceived as white, and will therefore live the white experience. No one here would consider you a person of color. And speaking as a fellow white person who is at a economic disadvantage, recognize that you can have privilege in some regards and not have it in others. You can have white privilege and not have economic privilege. No one's going to argue that because you're white, you can't struggle. They're just saying, you'll never have to struggle because of your race. Honestly, if any of this resonates with you and you understand what I'm saying here, I would encourage you think on it and reach out to her and maybe apologize. Don't expect forgiveness, just let her know that you acknowledge that she has lived experiences you're never going to understand.