Worried about Hen Party plans

Looking for some advice….
I asked my MOH to arrange my hen party (she offered and was happy to do it) and gave her the venue I’d like to go to.

I’ve just caught some info from a friend who is attending the hen and it seems some expensive decisions were made. Firstly the MOH booked a private dining area in the venue which has a £500 minimum spend, secondly she suggested a £300 minibus.
What’s giving me anxiety is that only 8 of the 11 people attending have confirmed. But despite this she has put the deposit on the private dining area. If people drop out, the ones who do come will have to pay more to meet the minimum spend. I could tell my friend was worried about this part.
Also really annoyed that my mum has been roped in to pay the deposit on the minibus and offered to pay for it all although no one agreed they wanted it (plus it’s massively overpriced).
I can’t understand why she’s tied us into some really expensive decisions especially when people aren’t committing. I was hoping for a girly afternoon food, cocktails, a few games and a dance but it feels like an expensive mess at the moment.
I don’t know what to do. Do I let her carry on planning or get involved?