Ask her out. At worst, she says no. At best, you go out and get a chance to get to know her better. And maybe things continue from there, or maybe not. Either way, you’re no worse off than you are now, and there’s a chance that you might be a lot better off. This is an imperfect analogy, but you can’t win the lottery unless you buy a lottery ticket from time to time.
When I was in my early 20s, I met a gorgeous young woman, a friend of a friend, who was also very nice and sweet, at least based on the few times I saw her. She was probably one of the most beautiful women I have ever met in real life. My friend said that I should ask her out, and I very much wanted to ask her out. But I was very shy, and I also figured that she was way out of my league, so I didn’t. Then a month or two later, another friend of ours asked her out. This gorgeous young lady said yes, and they dated for quite a while. The thing is, I would have said that she was way out of that guy’s league too, but evidently she didn’t think so. It made me wonder how many guys like me would have liked to ask her out, but never did because we thought “no way a gorgeous woman like that would ever go out with me.”
I’m happily married now, so I don’t have any regrets about how things turned out. But if I were in your shoes, knowing what I know now, I hope that I would muster up the courage to ask the girl out.