In that case, I might have feigned sickness. Or perhaps I would have gone to the bathroom, called a friend on a cellphone, asked them to call me back in two minutes (once I'd returned to the other people), I'd act like the call was a friend of mine in serious trouble, and I'd have to leave right away.
Ok. I wouldn't have lied to her. However, I almost always do have at least some other piece of food with me, be it an apple or a Luna bar or soy nuts. I'll have something, even if the other food is meatified. The sickness excuse, though, would work for me because the idea of me consuming meat makes me positively vomitous.
I'm sorry you went through that! Do you have a plan in place for the next time something like that happens?
ETA: I should have clarified: Do you have a plan for what to say the next time something like that happens? Bringing a dish of food to share is a great idea, but it doesn't often excuse you from the perceived "responsibility" of trying everything else.
Q: How many poets does it take to change a light bulb? A: 1001...one to change the bulb, 1000 to say it's already been done.