Riddler, sometimes you need to take a risk. Not knowing any details aside from what you just described, right now your relationship seems to me to be based on a false foundation. How is that fair to either of you?
She asked you if you loved her, and you denied it? You don't think there was the ghost of a chance that she might have had a reason for asking?
In what way has she made it perfectly clear that it will never happen?
No one can tell you what to do–and I'm not trying to tell you either. If you don't feel strong enough, you can't--but it seems to me you are selling yourself short. You deserve more. I believe that if you don't make the attempt to ask or try, you will probably regret it for the rest of your life. You deserve love in your life, and so does that girl. If its not going to be with her, then it's time to find out, so you can go out there and find the one it will be with. You never know though--it could work out. Maybe she wanted you to say yes back when she asked you--maybe that was her safe way to ask.
Tell her you like her. be casual about it. Let it just serve as a compliment, and don't press the issue. If its awkward, it will only be for a moment. You've been friends for years, 2 minutes of awkward will be fine.
I know a girl, and one of her best friends decided he was in love with her, and when she didn't feel the same, he just abandoned her entirely and they never spoke again. And that's lame. You can like a girl deeply and still just be friends.
You are worthy of love. If this girl isn't the one to give it to you, you ought to know, rather than angsting over it for months and years. (many people have been able to stay best friends even after they dated and broke up) Better for it to hurt tomorrow after having tried, than to still be wondering "what if" a year from now.
If you get a concrete answer, yes or no, either way you can move on and get past it. I've been in love a handful of times. Each time its been genuine and true. And losing the girl ultimately hurt... and then I moved on and eventually found someone else to like. One of my exes I never talked to again (mostly because she wasn't honest about the relationship in the first place) while another is still one of my best friends to this day.
You can tell a girl you love her, and its not the end of the world if she doesn't feel exactly the same way back.