I'm always wary of those who are "not ready for a relationship". It's an advance clue that you've about to get messed around.
What's her reason for not wanting a relationship?
Edited to add: I'd probably ask her to call you if/when she's interested in a relationship, then move on. Do not become 'friends' with her while you're waiting because you'll end up as nothing more than friens.
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.