Endorse fully all that Desire206 has offered up to you. Realize you know it's up to her and are giving her the support you believe she needs. Perhaps you need to ask her open-ended questions that allow her to freely express the emotions she is feeling. Instead of "why did you change you mind," ask her "what situation or sequence of events do you believe will allow you to control your emotions or apprehensions." This allows her to get in touch with her feelings and, hopefully, express and share them with you.
Also need to try and read between the lines. Is it possible her telling you she "might like it and want more" is her way of trying to get you to share with her how you'll feel about that, and why, IF she does like it and want more. Her greatest fear could be losing her marriage through this. If that's so then she probably needs reassurance from you that if she can't ever go through with it you'll still want to be married to her. And, you need to prepare yourself for that possibility.
It took years for us to take the step to participating in the IR lifestyle and even more years until we felt we were capable of handling any of the foreseeable issues that can, and in some cases do, arise from playing in this arena. It's not for everyone; for some, it remains nothing but a wonderful fantasy. If that's all it ends up being for the two of you, let's hope your marriage can survive that just as easily as you believe it will if it does come to fruition.