My sister is getting married and I am the MOH, however, one of my sister's bridesmaids and her mother offered early on to give my sister her bridal shower. She and my sister selected a date without consulting me or the MOB ( to inquire about any unavailable dates). When I was told the date for the shower it turns out it's the same weekend I had an out of town trip planned. I asked the hostess of the shower if there were any other possible dates considered, as I absolutely need to be at the shower. She gave me a very curt answer saying that it was the final date (this was 10 1/2 weeks prior to the selected date of the shower). I decided that I would have to cancel my trip and had no intention of saying anything to my sister. The hostess then proceeded to tell my sister (the bride) that I had asked the question, and that she thought it was rude and offensive. This upset my sister who was very upset with me for asking and told me I owed her an apology. I think it was inconsiderate for them not to ask me about my schedule since I absolutely need to attend. Am I wrong??