[aephi alum]

AEPhi's rule is that nobody except initiated sisters may wear the Greek letters. That goes for shirts, hats, lavaliers, keychains, everything. New members and non-members can wear things where at least the letter Phi is spelled out, e.g. "AEPhi" or "Alpha Epsilon Phi". A badge cannot be given to, or worn by, a family member unless she is also an AEPhi.

I don't have a problem with the idea of wearing other orgs' letters as long as it's clear that you're not representing yourself as a member of that org. Things like event shirts, "XYZ Mom", "ABC Legacy" etc are ok in my book. Block letters are not, if you could reasonably be taken for a member of the org (e.g. a girl wearing her older sister's sorority letters would be bad; a girl wearing her S.O.'s fraternity letters would be ok).