Hi Scarlet!

I actually have a legitimate reason for not eating sugar or a lot of carbs..I'm a diabetic. I can understand your discomfort, though, with people trying to got out of their way just for you. I didn't like it at first either. Now, I just take it as it's meant; a thoughtful gesture on the part of the host to make sure that there is something suitable for you to eat at the party as well as the other guests (which is what a good host or hostess should do).
There is a group of ladies at my church that hosts a tea for the mothers of young children once a month. After the first few, the hostess noticed that I usually didn't eat very much and inquired why. I was a bit embarassed and assured her that it wasn't that the food didn't look delicious (because it surely did!), but that I am a diabetic and can't eat foods so high in sugar or starch. Well....after that, they always had a special plate just for me, usually of the salad variety and you know what? Nobody else even noticed that I wasn't eating the same things that everyone else was.
The other suggestions were good too...offer to bring a dish that you know you can eat or a low carb dessert or just plan to have a higher carb day and get right back on track with the next meal.
You can't isolate yourself socially just because you don't eat a lot of sugar or carbs and most people don't even notice what you are or aren't eating unless you bring attention to it yourself.