Hen do question!

I'd speak to your MOH/BM's and let them know the story. Depending what they have planned, maybe the niece can come to part (pampering/something at home) then not come to the evening out/club/drinks part. If its an over 18's event, then I'd make it clear to your SIL. I think your SIL should have checked beforehand, before inviting her underage daughter along!

Another option it to just have a meal out with the BM's and neice, and not have her come to the hen do at all.

This. I'm sure your BMs won't feel like they need to plan the hen do around the 16 year old so just tell them the situation and they can let your FSIL know.

This. I'm sure your BMs won't feel like they need to plan the hen do around the 16 year old so just tell them the situation and they can let your FSIL know.

I suppose it depends what you're doing? How do you feel about her coming?

As someone else has suggested, could you do a separate thing with her like an afternoon tea etc.

Agree with what Teal said any way you could do something with her separate from the hen do? Dinner? Pamper session that way she will still feel involved xx

A lot of my family are tea-total so our plan is to go out for a nice meal or afternoon tea, and then the drinkers can go on to a bar from there but everyone still gets time together.

Could you do something similar with a nice afternoon tea with some mild hen shenanigans (loo roll dress etc) that she can come to and then those who want to have a boozey night can go on from there? If you're doing the whole sash thing she could still have that and get pictures with you all before you go out OUT!

To be perfectly honest, my initial reaction to this was 'why on earth would you have a hen do without all your bridesmaids'? Personally I would expect your BM's who are organising to take into account the age of the other BM and plan something accordingly to include everyone that you would want to be there. Hen do's don't HAVE to be alcohol fuelled parties - they can be fairly civilised. It's not unusual to have a future MIL or other relatives at a hen do that don't want to descend into full party mode (or that you don't want to have see YOU in that state) but still want to be involved, so I guess it's about planning something appropriate?

This!

Crikey.

My daughter was my only BM so I couldn't have had my hen do without her, although I didn't expect her to organise it! She was only 16 at the time but came along to the whole thing. She is very shy and quiet and some of it was a little loud and brash for her, but she coped with it and it was fine.

I would ask your OH's niece herself whether she would like to come and if so, then just let your adult bms know that she will be there. Ask them to be a little considerate of her age, and to make sure she will be allowed in wherever you end up going, but otherwise let her get on with it.

I had planned to do like an afternoon tea so they could all be a part of and was just aware as we are going to a cottage for the weekend it is a bit harder for her to bob in and bob out of activities