Sounds like more a people problem than a dog problem. Consistency i really key in a situation like this. I've owned and fostered many very food motivated dogs. and all have learned not to beg for food. (Goodies left unattended may be another story, but that's on me.) Like Robin, I have the HUGE advantage of being the only human here. I think it can be much harder to change the people's behavior than the dogs!
As for her barking if she' baby-gated out of the room, if you could endure ignoring her for long enough, she would likely stop, but she would no doubt escalate first, and, again, you would need the cooperation of all the other people present.