Hello and welcome!
Sometimes it's easier on a person when there's no choice to make, isn't it? Especially when it's a choice between what you WANT to do and what you SHOULD do. I'm sorry you're in this difficult situation.
Instead of giving you the stock answer, "don't do it!", I'm going to tell you that this is something you need to decide on your own. The only thing I can add is that I've never known a secret known to an entire chapter of sorority women to stay a secret for long.
Best of luck in your situation