I'm sorry you're so upset. You've gotten some great answers and suggestions. I think it is very important that your T knows that the chair placement is triggering you so much. Whether you write it or tell her or move the chair it's important because it's about how your past impacts you today.

I'm reading the book, Getting Past Your Past, and seeing that so much of how we feel in the present is because of incidents that happened in our past. We often don't know why something bothers us so much, but in your case you do. The only way to get over it is to work through it. That's why I think it is so crucial that your T knows yuur reactions. I don't think she has any idea of the chair bothering you. She's not a mind reader.

I know it's hard but you have to tell her. She doesn't hate you; that's how you feel because of things that happened to you in your past. I'm sorry you had such an upsetting session but it is "grist for the mill' as m;y T would say.