Do I reward or convince?

Ok, my Gf n I have been on a break, n we haven't "been" with eachother in almost a month now, I'm 18, n she's 17, she's graduating, n I just bought her a 700 dollar Tiffany necklace for graduation, on her grad night, if we don't reconcile intimately before than, I'm assuming we will just cuz I know she will want to the night of graduation, do I give the necklace before or after? My fear is if I give it to her before, it will feel like I had to Pay her, n rewarding her for not being with me for a month, if I wait till after, it's kinda like a reward in her eyes... Right??