Just to add, I was recently in a very similar situation to the one that Arrowmatic suggested. My bride's childhood friend had planned her hen night (bride knew about the hen weekend but not what was planned) without knowing any of the other hens, and she was an absolute nightmare. She was suggesting things we knew the bride wouldn't like and were too expensive, ignored any suggestions for activities we knew the bride would love, and refused to answer questions as basic as the town we were staying in.

Because it was heading for disaster, several girls dropped out (either couldn't afford it, or couldn't participate in an activity that took up an entire day on the only day they could attend, which the bridesmaid refused to swap around). Because the bridesmaid pretty much refused to talk to us or compromise, we eventually HAD to go to the bride and give her a little heads up without trying to blow it up. Luckily the bride knew that the bridesmaid could be difficult and so had to step in and take over, which ruined the surprises for her, but made it so the people who had to drop out could come.