I really don't have any advice to give you other than that it sounds like you are looking for some type of closure as well. You can't re-open a healed wound if it hasn't healed yet.
Your life is your own, You can't follow advice blindly. Especially since it's your love, not your friends or family. They can warn You, but I'd still try. I'd at least talk to her. I've had bad moments in my 7 month long relationship (also my first), but I've always tried to talk it over, explain things, find the problem and think about it. Even though I'm paranoid about her leaving me, I try my best not be controlling or to 'retaliate'.
Women expect things of You. She expected that I'd be just like other 17 year olds. Instead, I showed her all the respect I could muster, and that is a lot, not just opening doors now and again, I mean doing everything I can for her. Maybe your female expect other things from You? Maybe she didn't think you were actually in love with her? You know how it is, love sells today, it's become a brand, so not many people believe or hope for real love in their lives.
The only advice I can give You is to call her, talk. Maybe there's a chance to get back together, maybe she had some problems, maybe... everything is possible. I know that I'd regret not doing anything. But that is my advice, think it over, alter it, use it or dump it. It's your choice.