Here's how it would go in my chapter (and I can picture the sister who was president when I graduated saying this to a tee.) President would stand before the chapter probably before beginning the regular business part of the meeting but while we're in the more serious meeting mood. She'd probably say it just like this: "Ladies, we've had some instances of a few sisters discussing private chapter business with people outside of our chapter and I think it would be appropriate for us to review what can and can not be discussed with non-members. Ritual, of course, is never to be mentioned or discussed at all with any non-initiated member of Tri Delta, but chapter business is
also private and requires a certain level of discretion on your parts. Please be respectful of your sisters and keep our privacy in mind. Does anybody have any questions about what would be considered private and what is public?"
Senior year, I lived with two other members of my chapter and a fourth roommate who was a member of another sorority on our campus. She was our best friend and she even came with us to some of our events. Some people thought it was weird that she wasn't there at our senior soiree. By default, she knew pretty much everything about our chapter except ritual, because she was such a trusted friend. Tri Delta loved her and she loved Tri Delta and her own chapter too, of course.
Oh, and I swear that I didn't reveal anything secret in this post
