I wondered what happened to you

Hmmm... First you have to make sure that she is the right one to keep trying with, sometimes these things end for the right reason even when it hurts like hell, and rarely do they end cleanly with a handshake and a "have a nice day". Assuming you need to give it another go, for closures sake at least, or another valid run at a relationship then I think you need to look at what made her fall for you originally. Hopefully it wasnt money and buying her things; that is a red flag...
It isnt going to be any one thing that is going to win a girl back. Never. You can plan the greatest most romantic date in the world for friday night, but what about Saturday afternoon?
This is just my opinion and I am horribly old fashioned and will probably get heckled for this but here goes...It is all of the little things that you do day after day that make all of the difference, you have what is called an emotional bank account in a relationship; when you do kind loving things for the other person it is like making a deposit in that bank account; a little here, a little there. The account balance goes up a little bit when you open the door for her, it goes up a lot when you cook her a dinner(even if it isnt all that great- it is the effort), blow off your friends for a special night with her and it is a huge deposit in that account. It goes both directions though...blow her off to go out with your buddies time after time and the balance drops a bunch. Forget her birthday, it drops again.
The goal is to keep that account as high as you possibly can with every action. Of course there will be messups and argument and so on, that is normal over long term relationships, but it is the surplus in that bank account that allows you to weather the tough times; you can forget a birthday once in a while with no long term effects if you have been otherwise adding to the account.
Do you see where I am going?
I have been married for a long time. My wife Sarah is a beautiful woman who is fully capable of doing anything she wants and she too is old fashioned like I am. I alway open doors for her, I always open the car door for her. She has never had to gas up any of our vehicles since we have been married. Like I said she can, but she doesnt like to, and loves the fact that I go out of my way to gas up and wash her car for her. I get her flowers for no reason at least a couple times a month. I send her emails from the station(I work 24 hour shifts at the fire department) and call her when it is slow to say hi and tell her I love her. Lots and lots of little things; everyday showing that I am thinking of her. That way when I mess up I have done so many nice things it is not that big a deal. She let me go to take a bunch of high school fire cadets to a live fire training academy over our anniversary and it was no big deal to her because in her words she didnt have to save up for a year to get a display of love out of me. I had earned enough in my account to make a withdrawal and had plenty left over.
I am not sure how you can apply that to this girl; it may be too far past that point, once you start bouncing emotional checks it is too late and there generally is no recovery, but I have no idea what your situation is.
I wish you the best though...