Open Eyes, have I told you yet how great you are?

You're so wonderfully supportive. I appreciate all your words and help!
YES, my boss is a bully boss! And I am definitely her dammit doll, no doubt. Great description, fits so perfectly!
Unfortunately, she is the company owner, so it's not job security she's after, but I think it's power lording over someone else she's after -- like most bullies and abusive people. ARGH. I want to slap her one, it makes me so angry.
I do always remain professional, no matter what, so that's the good news, but her behavior (and snappiness towards me) irks me to no end --- she also LOVES to finger point and blame whenever anything is not done and it's even her own fault, and guess who gets the brunt of that blame? ME! Of course, given that I'm her dammit doll.
I'd like to confront her though -- how do I set boundaries without telling her directly that her treatment towards me is not OK? I can't exactly ignore her when she goes on one of her tirades.. like she did last week on me. I have to respond, and usually I find myself defending myself like some poor cornered animal fighting for their lives.
I'm also afraid of her at this point, and try to avoid contact with her as much as possible. I'm afraid of getting snapped at and demeaned in front of my co workers. I walk on egg shells now.... true sign of an abusive atmosphere.
So what should I actually say to her to set boundaries?