Joy, could you fit a drink or two into your meal calories for the day? Even if you got light beer or something and kept it separate. Heck, if you pour it into a glass, nobody would know you weren't drinking what everybody else was drinking, and you could always nurse it to make them last...You could employ the same idea for food. You could make something that would be healthy and just make a nice big plate for yourself and eat on that while you're there and bring some for the rest of the partygoers.
If you don't want to talk about your diet for the whole night, you don't have to. A little deceptive maneuvering can take you a long way.
Pauline, that "hot cocoa" sounds yummy!