I have a SIL who doesn't like me. I have no idea why. The only reason we have been able to figure out is that I am pretty friendly with her sister who she doesn't even speak to. She had a wedding shower that of course she invited me to, she wanted a gift. I went but I told another SIL I was going to have to start something. SHe told me to behave When I walked in I gave her a huge hug like she was my long lost friend. She didn't know what to do. It was awesome. Just walk in and give your SIL a big hug and shock her. It was priceless. I hugged her as I left too.