Sorry your sister got bitten. My hand was bitten by a GSD as a little kid and the same dog bit my sister too. But dog breed has little to do with dog bites. Small dogs bite and charge at people all the time, but since they are small, we think it's cute, not dangerous as it actually is. It has more to do with the owner and how he/she trains, handles and reacts that determines what a dog will do. Abused dogs or with bad experiences will also cause issues, as well as dogs that haven't been told how to act around other critters or people.
Both dogs are great with each other and great with the cats too. Kohaku is very mellow when it comes to other animals that are not dogs. He is iffy about people, but once he meets you, he's a giant lap dog. He grew up with Guinea pigs & rabbits running around.
Chillie on the other hand, is much more of a farm/hunting dog and needs to be supervised so she does not stress other animals or play too rough. She is a people dog, adores human attention like crazy, but at the same time, wants to be outside napping in the hole she made.