You should take the whole family in to the vet and have him/her tell them that she is overweight and that they can't feed her scraps. And go over the health problems of being overweight.
A lot of people don't realize it's a health issue and don't see why others care if a dog has a few extra pounds. It can be very humbling when the vet says your dog is overweight and that you're compromising the dog's health by perpetuating this.
A sortof intervention for the sneak feeders!!!
You could probably do this yourself, but they may not take you seriously. But if you just sat them down and printed out info from online about the consequences of having an overweight dog. Tell them that the dog will not live as long if she's overweight.
Regarding the tear staining -- there could be something in the RC that is causing her to tear. You could try a different food and see if it changes it at all.
Dogs are not our whole life, but they make our lives whole.