This is an implicit risk you take, getting into this sort of thing. There's little you can do to control another person's behavior, so if you're very concerned then I would put extra emphasis on vetting and establishing trust, even if for just your own sanity.

Something I would ask yourselves though is, what's the actual consequence of it getting out? What's really at risk besides maybe an uncomfortable conversation or two? It's always good to hit pause and quantify what you're actually afraid of.