Am I being that crazy girl?

My SO and I have been dating for two years. One of his good friends has a sister just a year younger than us. She has always been friendly to me but I have always though she liked me SO a bit too much. She features old videos and pictures of him on her social media. My SO and his friends went on a cruise last year and she went as well. This year she is going on a cruise with her friends and some of his friends and wants my SO to come with them again. I've looked at the texts between them and there's nothing really bad, but like I said, I've always thought she's been a bit too nice to him. Am I being THAT crazy girl and brush it off or is it something we should talk about?