Best friend to friends with benefits to girlfriend, breakup?

[Kharnage]

Here's the story,
So after I broke up with my ex in the summer, a new girl has came into my life and eventually became my best friend because she was there whenever I needed support whether it be with school work or emotional help. As our "best friend" relationship continued to grow we eventually became friends with benefits and finally we basically asked each other out, kind of. This all happened in the span of 2 months since my breakup in the summer. Now I'm going to admit that she is a wonderful best friend, but I'm not really attracted to her. Some of my friends says I can do better, but I don't want to hurt her feelings if I break up with her because she got me through so much and without her I wouldn't have been to where I am today. I want to go back to best friend level, but I'm scared that won't happen. What should I do?

*She is one of the nicest people I've ever known, and I'm not just saying that.
*She is an amazing girlfriend, but I'm just not attracted.
*She loves me a lot.
*Again, she is the ideal girlfriend.