Well regarding the original topic.....
The alumnae in your area stated they are not interested in supporting/helping you start a chapter at your school at this time. They are not required to, nor do they owe you an explanation as to why. It could very well be for reasons that only initiated members are privileged to know. It could even be for reasons handed down to the local alumnae from DST HQ. I'm afraid you may just never know.
I'm not a member of an NPHC organization, but I'll go out on a limb here and say continued pursuit of a DST chapter at your school, after being told no by initiated members may not be in your best interests. DST & NPHC members feel free to correct me if I am mistaken!