They were together for more than a year. They met at 16 and parted ways at 19. But you are right that the relationship they had then was much different than whatever potential relationship could be. It's part of growing up.
Once the explanation is laid out on the table, the ball will be in Troys court. He'll be the one to dictate what sort of friendship, if any, they have.
It won't be a short path either. Too much water under the bridge. They'll have to rebuild and start from scratch if that's even possible.