I have been an alum for many years now and I can tell you the things that bug me and why I'm not more supportive:
~Getting invites to homecoming festivities the week of. "Please come to the brunch that are having in your honor". Ok, well if you really wanted me there, you'd give me at least three weeks notice.
~Only getting contacted when they want money. We have zero newsletters from the chapter. We get one annual letter in August telling us a few accomplishments, then a two paragraph plea for money. I don't doubt they need it. I would be much happier to give it if I felt they cultivated me as an asset vs eyeing me as a cash cow.
~Feeling alienated when I do visit the chapter. I live far, far away from the house. I was back to visit a few years ago and the girls made polite chit chat, then went back to their groups. I felt not exactly unwanted, but sort of like people could care less whether or not I was there.
It seems as if actives don't realize the demands that we alum have on us. I don't expect them to, but I do think it's not unrealistic to schedule activities ahead of time. This year, I got my invite to homecoming on the day of

Perhaps they figure I live too far away, so why bother?
I have joined my area's alumnae association, but am having rocky success with that. I think it's important to note that most women want to have relationships with each other, regardless of their stage in life. However, always scheduling meetings in a singles bar doesn't respect those of us that are married.
Why don't you try hosting a tea in your home? More personal than a restaurant or bar setting? Or meet in the public place first, and follow up with a home setting.
Just some ideas.