There seems to be a bug in how RLS relates to firstnonblank/lastnonblank/selectedvalues kind of formulas. If you use one of these formulas on a table that is filtered by RLS, it will bring in data as...
DataDiva
Advocate II
Advocate III have a problem that in order to create a bridge table to set a relationship for the RLS to the main table, it's either a many-to-many join, or it has to go through another reference table. By that point, the RLS still doens't work through the relationship.
Microsoft really needs to fix this bug. I don't understand how you could possibly allow anything in the model to access data that should be filtered by RLS.