Does community property only apply to married people who live together?

My sister recently added my name to the title on her house. I am the co-owner of the house, and co-signer on the mortgage. My sister bought this house before I was married, but now I am going through a divorce. I live with my sister but have never made a payment on the house. I also have not lived with my husband for quite some time, although we are not legally separated. How will this affect my sister and I (and the house) if we are living in California?