My neighbor's smoked pork shoulder last year was so bitter from too much hickory. Your grandma probably used wet wood or let the heat get out of control. Smoking is a tough skill that takes a lot of practice to get right. I'm glad she switched back to casseroles because everyone loves those. The dog was smart to avoid it, honestly.
@laura841 makes a good point about hickory going bitter fast. Totally ruined a chicken that way myself. Found using dry wood and a water pan helped a lot. Keeps the heat from spiking and the smoke cleaner. Still a learning process but way better results now.
Wait, bitterness can add a nice depth if it's not overpowering. I've used wet hickory on purpose for a stronger smoke flavor that some people really like. It's not that hard to control the heat with a decent smoker and a little attention. Maybe that dog just doesn't appreciate good barbecue.