I'm not really talking about the stylistic concerns; I mean, they also didn't speak English with a British accent, and Artemesia was in no way a white woman.
I'm really talking about the decision to transform one of the rare heroic warrior women of history into a villain. She was strong enough to command marines. Smart enough to be victorious. And she was a queen in her own land. It's like the writers couldn't figure out a way to portray a genuinely powerful woman without making her a bad guy.
Yes, they took a ton of liberties with the history to tell an action tale. This particular liberty, however, was just another stereotype about strong females being the "enemy."
It's not a huge shock though. The whole thrust of both movies has been, Greek good, Persian bad. Neither film was particularly guilty of having complex writing. Artemesia fought on the Persian side and given that narrow focus of, this side good, this side bad, it's no surprise that she was a stereotype. There weren't many characters who weren't in one way or another.