Arabic is a language and Arabian are people.
And yes there are no blond Arabia not in that time at least if you read books. History books they descrip themselves like this: Dark-skinned/brown-skinned, with brown eyes, thick black hair, long eyelashes, kohl-rimmed (or deep black) eyes, sharp features, and a prominent nose.
Which is just the norm/dominant culture. It's like saying all Europeans are blonde with blue eyes. That's not the reality.
For the sake are arguing, there probably were blonde Arabians, but they were very uncommon due to genetics and environmental factors. Claiming an author is racist for making a girl blonde because it "goes against the dominant culture" doesn't make sense to me.
Girl that's the history if you don't like it complain to the dead people who wrote it.
And the Andalusians, Cordobans, Egyptians, Phoenicians, and Assyrians are not considered Arabs. Just in case you mentioned them. Maybe Muslims Invaded their countries but the ones who born from them are not arabians. They speak their indigenous language

Please tell me the blonde is not Arabian