I am mad at someone I live with and I'm not sure why?

I guess it has been a build up of things including how she talks behind everyones back. I think deep down I just think that I have been opening up to her too much and I don't want to give her "ammunition" so to speak to use against me. So I have just built up all of this anger inside of me which prevents me from speaking to her besides formalities. Is this healthy? Is there something I should do? Just even the way she speaks about me when I am right in front of her has an air of disrespect. I don't like being angry though....