What can i do?? My mom made sausages to eat today for lunch, (NOT hot dogs) and theres a barbecue this friday?

My mom made sausages (the normal sized ones) for lunch and dinner but i dont want to eat because im on a diet and i think it may ruin everything, AND im going to a barbecue this friday!! I dont know what to do now :/ i am about to be 17 5'6 weigh 140 pounds :/ and i do eat healthy even before i started the diet..