My friend with revealing clothes came with me to the Buddhist meditation. Our teacher wears traditional robes for monastic so she is not wearing anything revealing. There are certain ways however to show up for events with Buddhist teachers in this tradition. Being aware of the rules they have chosen to follow is part of it. I have worked with the monastic longer so sometimes I have helped teach people about how they live.
The reason to address her clothing was that her entire bra was showing when the loose shirt slipped down. It is both because we have been working on building her business as a coach and that there are protocols for attending these buddhist meditations. When I told my teacher and said I wasn't sure I did the right thing she (teacher) shared that she almost said something herself.