I don't know what to tell you, but I'm sort of in the same boat with my chapter. They didn't have an alum brunch last school year (which they've done every year since we started), so I wrote the CA about it and she never wrote me back. I was even going to give them money for the first time, but now I'm not so sure I will for a few years.
Does the chapter have other advisers? It sounds to me like they might need more. Then maybe the CA would have more time to write back? It's really sad, you've done a lot for that chapter, you deserve better.