Take a deep breath, girl, you addict sister is probably not feeling very good about herself right now and demanding attention out of fear.
Your mom is caught in the middle, and that's a nasty place to be. She loves you and is probably just trying to keep the peace as best she can. She too has a full plate dealing with your sister's addiction.
Quite likely, what transpired today wasn't really about you at all. You just happened to be there and catch the drama. And believe me, when an addict is in the house there is no shortage of drama.
I know when I get angry about stuff like this, I find trying to turn my anger into compassion helps me see things from a better perspective.
If you would enjoy Thanksgiving with your family, go. Maybe try your recovery "detachment" out and don't get drawn into the drama while you are there.
Hugs