AST doesn't require an advisor to be a member of the sorority. HOWEVER... chapter advisors need approval through both the chapter AND the national VP. Also, these advisors are not able to attend any kind of ritual. They are not considered members at all, and their access to information is very limited. They are only expected to help the chapter when necessary. But they are also well respected members of the Greek community.
To give you an example of someone who is an advisor of one of our chapters who isn't a member... David Stollman
http://www.campuspeak.com/speakers/stollman/
Please don't think that you can just "want to help students" and become an advisor for a chapter.
I became an advisor many years after becoming a member of my chapter, and I'm still learning new things every day.
This isn't a way into becoming a member of a sorority.
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