@Missingprincess - because Rose was another rich aristo and some papers like to print stories about upper class lovely ladies who wear expensive frocks well. Added bonus of her being Kate’s best friend for a while, or at least happy to be seen as Kates best friend to raise money for the charity she supported.
and then the women appeared to fall out. And the general tabloid explanation for women falling out is “argument over a man”. It could be something else, it’s probably something else. We don’t know.
perhaps think OP, have you ever fallen out with a female friend for a reason other than she shagged your man?