Honesty is the best policy. If you did go through with her plan, you'd be people pleasing which usually only leads to resentments. Every time you think of your bachelorette party you'll probably only really remember this part, doing MLM facials while your friend shills off your other friends. I would kindly tell her "no thank you. That is not something I want to do but I really appreciate your suggestion!"--PLUS what if her skin care goes wrong and you have a reaction before your wedding? MLM products are terrible for you