AITA for kicking my sister and her family out of my house after she shared a bed with her husband's brother on their wedding trip even though she said it was only sleeping?

My sister (35F) recently got married to her husband's brother's ex boyfriend's new husband's brother (48M) since they all grew up together and became close over the years. This is way simpler than it sounds because they all live in the middle east where divorce is very frowned upon and families like to intervene and help children get over divorce and grow together again. In this case, the brother and my sister fell in love during the wedding and decided to tie the knot.<br><br>Their wedding trip took place in Spain and since my husband (45M) and I (F) live in the US, we couldn't make it. However, we were planning to visit my sister and her husband in about two months.<br><br>So we offered to host them at our place since it's very large. My husband has since passed away and I live alone in the house, so I thought it would be nice to host them. We made all the arrangements and they arrived a couple of days ago.<br><br>The first night we had dinner and hung out, then they went to sleep. The second day my sister asked to see her wedding dress and she had a long conversation with me while my husband's brother watched tv.<br><br>The third day, my husband's brother went out for work (he has a remote job) and my sister stayed home. I had to go out for some work, so she was alone at home. She called me and asked if I could bring her something from a store and then she told me that she is sleeping in my husband's bed and my husband's brother is sleeping in the guest bed with his brother's wife who is my cousin.<br><br>I was very surprised and asked her if that's okay with her husband. She said yes. I asked her again because I couldn't hear her and she repeated that it's okay.<br><br>I arrived home and they were sitting in the living room. Her husband's brother's brother came from out of town and he was also at the house but he left after a few hours, so it was only my sister and her husband.<br><br>I couldn't believe she would say that sharing a bed with her husband and his brother's wife's husband was okay. She started yelling at me and saying that I'm embarrassing her in front of her husband and that she's telling the truth. I said that they are sharing a bed. She said no, his brother is sleeping in the bed next to them and they are sleeping in the bed. I asked her again and she said no again. I told her that she's crazy and that they are definitely sleeping in the bed and that she's an embarrassment. She said that if I embarrass her more, I'll regret it.<br><br>After this argument I went to get her thing and left her room. A few hours later we had dinner and hung out. Then we went to our rooms and I asked her husband to come to my room because I found out that his brother and his wife were sharing a bed with my sister and her husband and that they didn't mind.<br><br>He was very angry and asked her. She said the thing again. Him: "Did you share a bed with the three of them?!" Thing: "No! We slept in the bed!" Him:*slaps my sister so hard she fell on the floor and he left the room. I asked her why she insisted on sharing a bed with her husband and his brother's wife and her husband. She said that it was none of my business and that I was a jerk. I told her that she's not welcome anymore and if she didn't leave with her husband, I would call the police.<br><br>She said fine and left with her husband. They aren't anymore at my house but they haven't left yet. They are just in the lawn. My cousin called me and yelled at me for slapping my sister and hitting her. I told her that I didn't and that I just told them to leave. She said that my sister looks all messed up and that her husband slapped her. I told her that she had shared a bed with two men and that this is a messed up situation that doesn't need her husband hitting her. She said that I'm very bad for not helping my sister and that she won't talk to me again.<br><br>AITA?