Then just forget about her and move on. I wouldn't wait on someone to start dating, and I wouldn't date someone in order to make someone else feel bad because it's likely she doesn't give a hoot enough to worry about it if she keeps telling you no. Just forget about her and move on. Not worth the worry.
I had a girl once that I was friends with and all was superbly good, and I discussed moving further in the relationship, but she said, "I don't date friends." I said, "So, what then? You'll date a stranger? At least you know we have much in common!" This was even after I had taken care of her for 3 days while she was sick. She said again, "I don't date friends, and I hope this doesn't come between our friendship." I said, "Nah, it's fine."
Well, I started seeing other gals, and she got totally miffed about it and called me screaming in the phone and hung up on me. Apparently, I was a horrible friend for not discussing my private/dating life with her and for "settling" for just "any ol' girl." This was one of those "wants the cake and icing, too" deals.