Some quick background: DH were married in March after 6 years of dating. His parents and I have gotten along perfectly since day 1. I love them so much and couldn't have gotten luckier. I definitely feel like their blood child and they treat me like one. I also get along great with DH's brother. His sister however, has simply never liked me. She has constantly competed with DH. Anything he does, she has to do too. She is currently engaged to a man her parents are not at all fond of. Their negative reaction to their engagement has compounded her poor treatment of me. The months since out wedding have been unbearable, to the point where I avoid family gatherings.
Last Sunday, after several weeks of odd behavior from my in-laws, I asked them if anything was wrong. I couldn't recall saying or doing anything offensive and neither could DH. His mom hesitantly said they had discovered something about my past that they were not happy about...because I kept it from them and my husband. She proceeded to tell me that my sister-in-law figured out that I had been previously married, which is completely untrue. I've dated DH since I was 18 and only dated three other guys prior to that. I set the record straight and my MIL and FIL seemed to believe me, but I feel as if the damage has been done. This viscious lie has forever changed my relationship with my in-laws. Because I have never been open about their daughter's poor treatment of me, I cannot point to it as motivation for fabricating such a lie.
Her wedding is coming up and I have decided I am not going. I do not feel I need to support someone - family or not - who behaves this way. It could just be my anger talking. Am I out of line?