OK, I just can't seem to let this one go.
Be at ease.
You're right that telling her how I feel would leave me with the fewest regrets. I'd know exactly where I stood, and I would be proud of myself for speaking up. Where I'm having trouble is that IF she likes me, continuing to date someone she's not as interested in doesn't speak a lot for her character, though I think it's more likely that she sees me as just a friend. In the end, I think I'm too proud to beg for reciprocation. I'd rather it happened more naturally.
It will hurt for a while, but probably mostly in the ego, considering who's being preferred over me. But it's fine. Life has its disappointments, and then it has its real tragedies. Thankfully, so far I've only been disappointed.