The reason Batrgirl outstrips KF agaianst the higher tiers imo is that she has a million ways to confirm into vortex. Random b1, b2, j2/3, MB teleport, d2, MB flying bat, etc. Also her cartwheel + flying bat + tele give her much better midscreen space control. And Batgirl has much better control of interactibles in a game where interactables matter.
If you can stay away from or jump away from KF's slide, or outzone/counterzone her, she loses most of her space control and has to take a lot of risks in order to try to play her game. That's ok against characters who have to struggle with it, but not that great against characters with better mobility and space control.