AITAH for refusing to eat with my family?

I (19F) have selective mutism, a severe anxiety disorder that makes it impossible for me to talk in certain social situations. It also extends to other things like being unable to use public restrooms or eat in front of people. Because of this, I often skip meals rather than eat around others. I’ve been in therapy for 16 years, tried medications, hospital visits nothing has helped.

Every year, my family makes a huge Christmas dinner with 50+ people. This is my worst nightmare. The noise, the conversations, the expectations, it’s all overwhelming. I physically cannot eat around them. So, my routine is usually to grab my food quietly and eat alone in my room. This year, my family insisted I eat with them, saying it’s “rude” and “selfish” to isolate myself. My parents told me it hurts my grandmother’s feelings because she wants to spend time with me. They also said that after years of therapy, I should at least "try" to eat at the table. I told them (through text, since I am non verbal) that I just can’t, but they don’t understand.

At dinner, when I got up to take my plate to my room, my uncle made a comment about me being “too good” to sit with the family. My parents sighed and told me I was being difficult. I just froze up, took my food, and left. Later, my cousin texted me saying that while she understands, I should have “just sat for a little while” to make my family happy.

Now I’m feeling guilty. I know my selective mutism makes things hard for others to understand, but I don’t know how to deal with it.