No one is really "accusing" her of appropriation, she has appropriated things, but cultural appropriation is a neutral academic term and something that happens everywhere. And her having a parent or grandparent who was born to Russians or even in Russia before moving away doesn't change anything about how she constructed the world of her books.

(The fact that you have some ancestry from a country in which you never lived, whose language you don't speek, and with whose culture you have little connection, does not make you magically of that culture - this is one of more tiring American myths - if you ciltuvate this culture at home, than yes, but the mere fact of birth of your parents or grandparents - not really... I'm honestly baffled when people tell me I'm Russian too when what they mean is I have some percentage of Russian blood - it' in no way the same as being Russian in the sense of living and growing up in the country.)