We are having a very small ceremony, with just our parents & grandparents...But, we are having a reception/party at our new home where we plan to invite around 40 people. Part of the reason I chose to have a small ceremony is because my family does not get along well with one another. My parents have been divorced since I was 7, and are marginally civil to one another. My mother has a serious temper, no tact, and little self control. My older sister is an alcoholic and has, in the past few years, lived with myself, my mother, her ex-husband, her kids, and a few boyfriends. Each time she moves, it is because she has reached the end of how much that person can help her, and it usually ends badly. She lived with our mother for a couple of months, and then left on very bad terms. The two of them are not speaking, and, after 3 months, still very angry. Additionally, I have not heard from my sister or her children since the blow up with my mother. I have no idea where she is living currently. We are about to send out the invitations to our soiree and I have no idea what to do when it comes to my sister. I have to have my mother there. My fiancee's entire family, including his two sisters & their children, will be there. Ideally, I could invite her, and she would not come, with a reasonable excuse. However, if she does show up, an ugly white trash cat fight is entirely possible, between her & my mother. I hate that I cannot trust my own family to behave for a couple of hours, but I REALLY don't. But, I hate cutting my only sister out of such an important day. I THINK it would really hurt her feelings, but that kind of depends on her mood too. Any advice?