There are design rules for a reason. They're not just arbitrary things that someone just made up out of nothing - the human brain has preferences for visual stimulus so things like the "rule of thirds" are based on how people prefer to see things.
So yes, her opinion has more value because it's backed up by proven design rules. It's not as subjective as you're implying.
So yes, her opinion has more value because it's backed up by proven design rules. It's not as subjective as you're implying.