I can understand your anger.
But I think your sister does know something is wrong, thats why she took you to a T.
It's her way to try to help you. You have admitted you have some problems, is it so bad to go and get help from a T?
It seems your sister cares a lot about you and wants to help. You said talking to the T was liberating, thats good. Be kind to yourself.
Thinking of you.