You definitely need to keep your bunny away from cat food. Their system is not set up for what's in most carnivore diets. It can cause an dangerous imbalance in their digestive tract causing a serious case of gi stasis. And even if your bunny's digestive tract doesn't seem to get bothered, then the dangers over time can be fatal -Over time, the high protein can cause kidney failure.
Here's a link to more info: http://www.veterinarypartner.com/Content.plx?P=A&A=502&S=5
So, for now, watch your bunny very carefully, and make sure she eating and pooping normally, and if you see a slow down within the next 24 hours, call a vet. Make sure she eats plenty of hay, and keep away from treats right now to be sure the the bacteria in her intestinal tract remains normal.
And you will need to feed the cats in a place the rabbit is blocked off from. Can the cats get to a place thats high enough, that the bunny can't get to? Like a kitchen counter?
Let us know what you come up with as a solution. I'm sure there are others that can benefit as they could have the same issue.
And if anyone else has cats, do you have tips to keep cat food out of reach of your rabbit?