I don't know why I feel I can't do this.
Maybe I must put my granny panties on and do it for the greater good.
Even though it will probably attract all sorts of vindictive blowback in the short term.
Well, I suppose don't make it obvious that you have the answers, lol. Ask who are in charge of the company, and if Cheri's name is mentioned, say "hang on a second, why does that name sound familiar?". A quick bit of fake googling and you come back with "ummm, she was at the top of the BTC Global bitcoin scam".
When they start talking about profits, ask them how compound interest works. Hopefully they'll actually give you a correct answer, at which point you can do a quick little bit of maths and point out how this "investment" couldn't be sustained.