Why do you have to be tactful? She isn't!
I'm a vegetarian and haven't used body shop since they sold out ethically many years ago. I would be making no bones about telling her I wasn't interested, the majority of the group aren't interested and if we wanted what she's suggesting we'd have asked! Not to hijack the weekend and leave the body shop crap at home
I'm guessing the 2 "in favour" are naive and unaware that what they're actually going to be getting is an awkward evening of hard sell they can't escape from! Have you warned them?
Me, I’m a gob shite, too long in the tooth to participate or entertain anything not of interest to me.
Yep same! Refreshing and liberating isn't it? 
Surely it can’t take all evening?
With mlm? Ohhhhh yes it can with lots of high pressure to buy/order then and there!
that she’ll be ‘taking orders for gifts so don’t forget your wallet ladies’
See?
This will likely be multiple times DAILY in the run up to the trip, then even higher pressure on the trip!
I won't give body shop any money since they were so unpleasant to JK Rowling.
Another Damn good reason!
How about "not my thing as I don't support body shop for ethical reasons I don't wish to detail. I also think this is a weekend for friendships and leisure and think all work related activities need to be left at home to enable us all to properly relax"
?
Re "how the hell do we stop this?" Is your in!
Ask the others to be HONEST if they're genuinely interested out of the group of 8 that means only 3 actually are "in favour" - her, her gullible husband and someone who prob doesn't understand it will be a sales pitch!
Strength in numbers - if as a group of 5 you say to her "nope" then she hasn't a leg to stand on if the majority rules!
It's also not on to turn it into a "women v men" night when everyone is there
The men'll be getting pumped for orders at some point too, no doubt.
I agree - prep dh!
Another of the group has just replied using the skin allergy line
Is that same one as said " how do we get out of this?" Or a different person?
Let her huff! She's the one that caused the awkwardness!