When I was an active, my chapter always supported other sororities' philanthropy events. Generally, if (say) AXO were holding a lip sync contest (that was what the AXO chapter at my school did as their major annual fundraiser), every other sorority would enter an act, plus every sorority and many fraternities would buy "house tickets" - the GLO pays a flat fee and anyone in the GLO can attend. Chapters would then return the favor - AEPhi would get a house ticket to AXO's fundraiser, and in turn, AXO would get a house ticket to AEPhi's fundraiser.
Additionally, sorority members attending other sororities' fundraisers were encouraged to wear their own letters to show Panhellenic support.
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When I was a senior, I attended a fundraiser for a sorority on campus. I dragged my then-boyfriend / now-DH along. My sorority had a house ticket, so I got in on that, and I paid for his admission. It was an election year, so the sorority ran an impromptu political impersonation contest. DH does a great Ronald Reagan, so he got up and did an impersonation, playing off on Reagan's Alzheimer's disease. He won the contest. When he sat back down, I whispered in his ear that his impersonation was oddly appropriate, as the sorority running the show was Sigma Kappa and their philanthropy is Alzheimer's research. (I have since gathered that it's gerontology in general.) He thought I was kidding.
The kicker was that after the show, we ran into some of his friends who had attended. He introduced me as "my girlfriend Nancy". Given the Reagan impersonation, they did not want to believe that my first name actually is Nancy.
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