My cat thinks she's a human...that, or that we're big cats (which is probably more the case, because I think I bat at her as much as she bats at me). She's constantly popping out of nowhere to attack. I definitely wouldn't leave her alone with my hedgie. She attacks us, let alone something smaller than her. The only interaction time they get is if she comes over to investigate while I'm holding Quentin, and then it's only a sniff because she freaks out and backs away when he huffs at her. It is from her that I get full understanding of the saying "curiosity killed the cat" because two seconds after she just freaked out and ran away, she's right back over there trying to see again. :roll:
Any interaction your cat has with your hedgie should be supervised, for sure. And if it seems to stress your hedgie out too much, keep it to a minimum.
Put the cage in a room with a door you can shut to keep the cat out. One day I was cleaning Quentin's cage and left the door open. The cage is two Sterlite containers hooked together with PVC pipe, so I was cleaning the play area part of it and I set aside the part with the food. When I turned around to get that second part, the cat was squeezed in sideways (I don't know why, but she chose to situate herself in there the shortest way of the bin) eating the food that was left from the night before. As amusing as it was while the cage was apart and on the floor, if she'd done that while the cage was together she could've knocked the whole thing over. So you really have to be careful about your cage set up when you have cats.