pyramid scheme

Kristy
My sister invited me to a "business meeting" and told me to refer my friends and bring my  hubby/daughter..pregnant on a school/work night. Being rather aggressive about it too. 🙄 
She sent me the link, and it's a total scam! And initially she said she'd like my support, but in reality it's for her scrub boyfriend who I'm not a fan of in the first place. If I decline, she's gonna guilt trip me and if I tell her it's a scam, all hell will break loose. 
The passive part of me just wants to sit through an hour of this bullshit and decline later. Or just tell her I don't feel well the day of. Husband says I should be upfront with her now and tell her to steer clear from it too. Any advice?