We were having a really nice evening planning a birthday party for our other sibling but arguing a little bit throughout.  It didn't seem like anything major but she thought she detected a "tone" as I was putting groceries away in her fridge.  Suddenly, she yelled at me to "get the fuck out of her house".  I was completely shocked and bewildered.  Not only did we have a lot more planning to do but it was just so rude.  And the evening was kinda fun before that.  So I start gathering my things, etc. and she is just shouting and shouting and shouting at me to get out.  I am becoming increasingly more angry that she is treating me this way and can't seem to find all my things, she is taunting me and asking me if it feels "big" to be staying in someone's house where I'm not wanted.  I am trying to explain to her that I am just trying to gather my things and she is opening her door and screaming at me to get out.  I get my bags and she is shouting (for all her neighbors to hear) for me to leave and get the fuck out and I am feeling more and more anxious and hurt and just shocked and so I slapped her and told her to stop it, then left.  Part of me doesn't even feel bad about slapping her but I know it was wrong and I just made things worse.  I am just so tired of the mood swings - I feel like 50% of the time we hang out something like this happens and I am only able to take so much.  I haven't reacted to her swings like this for about a year.  But I am FED up.  And normally we could just take a break from each other but we were supposed to be hosting our other sibling's bday party at her house tomorrow.  I just feel terrible about the whole thing.  Not really sure what I'm looking to accomplish by posting this but it does feel better to not have it swimming around in my head. 