Wedding Ettiquete

I have a question. There is this girl (Kelly) that I work with that I had invited to my wedding last October 2006. I remember we were always talking about my wedding and she always had a billion questions for me about it. Well she did attend my wedding. She got engaged a few months after me and she told me all about it and made a big deal on how excited she was. Well, her wedding is this summer (2007) and I found out that she invited 3 other people in my office but she didn`t invite me. I felt a little hurt because I thought that for sure she would have me as one of the first people on her list since I invited her to my wedding and because of our involvement at work. ON TOP OF ALL THIS....one of the girls at work that she had invited to the wedding (Helen) sent out an email to a couple girls at work trying to invite us to a bachelorette party for Kelly. I was really offended at that point. Helen even told me that Kelly knew about the bachelorette party she was planning and that made it double wrong! How dare she first not invite me to the wedding and then try to get me to come to her bachelorette party with a gift? Is this wrong of me to feel this way or am i over-reacting? Isn`t it rude of her to do this? Should I have expected an invitation? Thanks.