In the US we have bachelorette parties and they are essentially the same thing. A get together of the bride and some of her close friends before the wedding date. A last fling.
The last one I went to, we went for pizza and a movie--the bride, her sisters and sister-in-law, her step-daughter, if I remember correctly (she was 16) and me, the mother of the bride. It was pretty tame. The pizza may have been good. The movie--The Time Machine--was pretty good but kind of scary.
While we were in the UK we encountered several groups of young women out on a hen party. And let me say, if the ones we saw were typical, they really do it up as a doozy of a do. How did we know the groups were hen parties? Have a look at this group of young ladies we met at Hexham while waiting for a bus up to Hadrian's Wall. We ahd no idea what was going on. this group had arrived in their own coach--a dozen or so girls in bear suits. We had no idea what to make of it. the lady from Once Brewed who was waiting for her bus home (or was she from Twice Brewed?) said, "Oh, it's a hen party!" and got them to pose for me.
Goldilocks--the bride--and some of her group of a dozen or so slightly inebriated bears.
In London, it was angels and devils.
H is for Hen Parties.