For starters read the lists of toxic/poisonous foods, plants & meds here (especially the 3rd post re: foods). Print it for the whole family and get them to understand that even small amounts can make them very sick or die.
http://www.yorkietalk.com/forums/eme...oods-misc.html
Also print a list of safe foods for treat. Grandpa can give her green beans, carrots, small bits of apple, a few Cheerios, etc. instead of meat bites. I understand that people want to give treats, so make sure they are the right ones.
Another thing, tell everybody who has access to your pup that giving her bad things could make her very ill and end up with vet bills in the hundreds or thousands of dollars. So whoever gives the treats should be made responsible for those bills if they insist on giving them bad stuff.