Don't be so quick to dive overboard out of the sinking ship, as it were. I for one lost my fraternity membership mainly because I stopped being in touch with most of the people (well, the fact that I wasn't attending the college for a while didn't help, either). Have you tried other options? It may be all you need is a few good socializing events with your fellow sisters; the SDT chapter at Emory University (DE chapter, I think) is really close, and one of the main reasons I think that is so is because they are constantly doing events that involve all the sisters. Perhaps a bit of initiative on your part can redeem the sisterhood in you and others of your sisters' eyes
But, above all, you should never feel like you're confined by a sisterhood, that's not what it's about. If you truly feel that way, I doubt there's anyone here who would object to your getting out of the situation. Sometimes speaking to your fellow sisters from other chapters or even total outsiders who are simply familiar with the organization vicariously can help. Send me a PM if you need an outside look at things