Strict Vegetarian Thanksgiving in a VERY southern home?

My husband and I are strict vegetarians for health and ethical reasons. We mainly eat organic produce and the occional organic dairy item. We do not consume anything from animals such as chicken broth, gelatin, ect. and tend to consume a lot of vegan items. My issue is that we have been invited to an out of state ( 13 hours away) southern style, traditional, formal thanksgiving. The hostess is my hubbys grandmother who we have not seen in years. She is a very strict, almost mean lady and to be honest kinda scary. The last time I was at her home, she got VERY mad at me, and that was the first time I met her. We have informed her of our dietary issues. Im not so sure she took to kindly to the news. Now my question is that we have already RSVP'd ( in order to be with family with have not seen in YEARS), and Im not sure if we should bring our own food to prepare, or prepare something at a hotel or eat something before going. I mean, I could adjust anything we make to be meat eater friendly ( as in no tofu or anything considered weird). I just dont want to disrupt Thanksgiving by offending her or anyone else. Food gatherings are very important where we are from and family coming together is important to us. Someone please help...lol.