We need to know every ingredient and amount of each ingredient to guesstimate. The fat used in cooking and dressing alone could be 300 calories or more.
In these situations, if I have a purse (almost everyone does
) I can make my own food and put it in there and the problem is solved. Otherwise, I either don't eat until after, eat before, put a "food bar" in my pocket or bring a meal replacement shake to drink to avoid feeling pressured to cave with limited food options.