Good luck, Jess! Can you prep healthy meals on the weekend and then you have a ready selection to take with you for good lunches and ready-made dinners? When you have the desire to get healthy, sometimes it doesn't matter what those around you are doing, you can steam right ahead and do what you know you need to do. They'll probably join in down the line, if they realize that they cannot sabotage you
Make a listing of WHY you want to lose weight. Why is it important for you to do so. Refer to that list often to help you stay focused. Good luck!