Definitely bring your own dish to share and don't eat the pasta. Don't let anyone sabotage you for any reason. Don't take it personally that people are noticing positive changes. Think of it that you might be a good influence on their lives and stay strong. The dinner is not about eating pasta, it's about saying goodbye to a friend and it should be about them. Let the food only be a problem for other people. Your solution, you already stated, bring something healthy to share. Don't tell them you're on a diet, tell them that you've changed the way you eat. It might get them thinking, especially since you've shown results.