I think they don't like her for similar reasons to the royals not liking Diana--she steals the limelight. I'm sure race and gender play a role, too, because Britain and other Western nations are historically and institutionally racist and sexist. All of these royals are pitted against one another since they are born into a ruthless system in which the winner gets to be King/Queen/Princess and gets the money and power. It would screw almost anyone up. Outsiders aren't welcome.