Etiquette Question

[lasttime1999]

I am non-greek, and I have an etiquette question. I have several friends who are members of Delta Sigma Theta Sorority, Inc, and they invite me to chapter events. When I attend these events with them, some of the women assume that I am a member of the sorority before I am able to tell them that I am not. What is the most polite way to tell them I am not a member? I have said "oh I'm not a Delta", but feel like I may offend someone by using the term "Delta" instead of "member of the sorority" or etc. I enjoy attending the events and don't want to risk not being invited back because I was disrespectful.

Thank you for your advice!