@Ojwasguilty,
She is clearly open to reconnecting. My advice.
1) Apologize. Saying that you know what you did wrong and that you have changed will go a long way to reassure her.
2) Once you have apologized, let it go. The past is the past. If you both want a new relationship, your goal is to build a new, more mature one now that you are adults. You shouldn't be too hard on yourself... teenagers are not known to be emotionally mature. If she is willing to try again then go for it.
3) I feel I need to comment on your statement that "I would never leave again". This may be how you feel... but it isn't realistic. People change and for you to promise to be with her for the next 50 years is not reasonable.
The healthy thing to say is that if she lets you back in, you will treat her with respect and build a great relationship no matter what happens.
You are about to build a new relationship after both of you have had time to grow as people. The best relationships are built carefully, learn about who she is now, communicate your feelings, listen to her needs.
Part of emotional maturity is realizing the relationships are about honesty, communication and respect. They need to be built.