You've gotten some fantastic advice. I was initiated into my sorority over 25 years ago. The 3 years that I had in college were great, but they were only the tip of the iceberg in my sorority experience.
Our alumnae group is active in assisting the local collegiate chapter and we have great activities together at least monthly and usually more. For me the philanthropic activities that we do give me an incredible amount of joy. While we are not as active as a collegiate group, we come close.
When those on here tell you that your sorority is a lifelong experience, believe it. Look at your decision against the backdrop of the next 50 years, not just the next 3 months and see if that puts things in a different perspective. Stick it out...you will not regret it.