Never heard of this being a side effect. Most Liver Shunt dogs I know are on Metro AND Lactulose and low protein diet. K/D is usually NOT used becuase it has pork in it, and that little bit of pork can cause neuro (HE) symptoms in Liver Shunt dogs.
Has you look into the ROYAL CANIN Veterinary Diet® canine HEPATIC LS™ 14
HEPATIC LS | Royal Canin Veterinary Diet
Here's another thought, did you have to give her any shots/vaccines to board her? That could have set off the HE too
