Extremely pissed off 😡 please help😞

So me and my finace wanted to do a destination wedding in Jamaica but his sister didn't want to go so we chose to have our wedding where we live next year, we just found out her and her husband are going to a coworker she hardly knows wedding in Jamaica literally a week before ours because she doesn't have to bring her children with her.....she's also not attending my bachortlet party because she doesn't want her husband going out with her brother ...and now she's complaining about the price of the bridesmaid dress....if this was all her stuff she wouldn't give two shits and tell the person off. She's extremly selfish and expects me to change everything for her and she's 7 years older then I am 😑 also 6 months Preg here so I'm running very low on patience with people 😭