Well no. That's how Kate was written. It's not how she was played. But like I said, you're seeing something a lot of people aren't. And to be fair, I'm sure a lot of people are too, it's all subjective in the end.
The thing is, I don't consider myself an acting snob. I've been watching telly and movies for a long time, very little of which would be considered highbrow entertainment (seriously, I really enjoyed the aforementioned Birds of Prey) - and from the thousands of performances I've probably seen, across all those shows and films, I honestly couldn't pick out more than a handful of actors who have ever been bad enough to take me out of whatever I'm watching.
But Ruby is one of them.