ARG! This is so frustrating, I know exactly what you mean... my situation was a little different, but I feel your pain entirely!
Three of my sisters (Lisa, Kathleen, and Rachel) and I were all officers in the School of Theatre Student Advisory Council - which was already kind of strange, because we made up over half the council, and since we're friends I think it made other students and officers feel left out - so it was hard to try to keep Kappa stuff out of SAC and vice-versa. But Rachel CONSTANTLY brought up stuff that we had done with Kappa, and how we should try it with SAC - and they were just awful ideas, things that would never work with SAC simply because of how completely different it is from a social sorority! (SAC was basically formed so Theatre students had a voice with the faculty - we also ran an ongoing community service project, had BBQs and parties, ran a student-directed theatre season - kind of like Student Council in high school, I guess)
Lisa and I really didn't know what to do - Rachel would keep bringing up Kappa stuff at SAC meetings, no matter how much we asked her not to - and all the other officers would roll their eyes and it made things very difficult... we never really came up with a solution, so I just wanted to say I totally sympathize with you!