Talking

I've been trying to get up the courage to talking about treatment of me at home.I live with my sister, and the relationship is like our parents and that bugs me. I set up an action plan to talk to her, but I keep finding excuses, being to tired, lack of time, and not wanting to be in the same room with her. This is getting on my nerves. It's like the big elephant in the room that I can't find the right words to actually say. This shouldn't be hard but, she has turned into a bully for me, and that triggers me into being passive, instead of being proactive. But I just don't see the point... there's so many assumptions that she has made that have hurt me. How can I tell her that??? Telling my T was hard enough that I cried after the session last time. How do I know that it will turn out okay??? How can I bring up the topic when I know that she is stressed about the future? She has her own problems but the problems are getting too me. How do I start talking??