Should Bridesmaids attend the Bachelorette Party

Hi! My bachelorette party is in one month. My MOH has asked everyone for their availability and confirmed with my bridesmaids on the date and how the trip would be split between the bridal party. One bridesmaid said she can’t get the weekend off anymore and will not be able to attend. I know it’s selfish but she has done this to my other cousin. She did not attend her bachelorette last week with a four month in advance notice and is not attending her bridal shower either. I don’t want to be selfish but I do want to talk to her and ask if she wants to continue to be a bridesmaid. I don’t want to have to pull teeth to get her to participate in events. I know bridesmaids are support for the bride. Am I being dramatic? I don’t want to cause trouble if I am just being dramatic.