Everyone can - and often does - have confident opinions about those questions. But you can't really answer them in any objective way unless we can agree on a definition of the word.There are basically two categories of definitions:The interpersonal definitions. Something like "Prejudice or antagonism directed against another person based on their membership in a racial group."The sociological definitions. Something like "A highly organized system of 'race'-based group privilege that operates at every level of society and is held together by a sophisticated ideology of color/'race' supremacy."
“Eliminated the idea of personal racism” is kinda an overstatement isn’t it? Like yeah, it exists, but interpersonal racism against white people just doesn’t do anything, or at least nothing worse than any other kind of insult like calling them an asshole. It maybe hurts white feelings a little and that’s it, but most white people don’t even seem offended by terms like “Mayo monkey” or “cracker” and I would guess it’s because those terms aren’t representative of white people being systemically oppressed for being white, since that’s never been a thing. There’s an important distinction in that things like N word or the propaganda trying to paint black and brown people as being criminals is literally tied to slavery
Basically, these kinds of disagreements boil down to there being two ways to define racism: a colloquial definition, where racism is just treating someone differently due to their race, and a more academic definition drawn from the social sciences and philosophy where racism is, to use the standard simplification "prejudice plus power."
You're using the first definition, on which you are correct that it appears to be possible to be racist against white people; and your sister is using the second, on which she is correct that it would seem impossible to be racist to white people, at least in the context of a society where whites are and have historically been in a position of power over other racial groups.