I lost someone young too though with far different complications than what you have. I can say too that while it has lasting affects, the problem with my relationships has not been any sort of promise, but rather the idea of other women not measuring up.
While your promise is noble, I think you should void it. Why? because there is no marriage in heaven. I imagine the woman who died would want you to have a chance. I would confess that promise as a sin, and try to move on giving yourself at least the option for marriage. It seems likely you are hardwired for marriage, so trying to short circuit that now is going to result in some pain for you. In your confession, I would tell God too that you are sorry you made that promise too if you did not consult with Him. Chalk it up to trying to do the right thing, that ended up in tragedy, but please don't carry that tragedy much further. Honor her life by remembering her and learning to grow in Christ with all that God can bless you with including a wife and family.
As to comparisons of her to other women, you will be able to overcome that. You have to see your role and any future woman you date from God's perspective, not yours. I will say too that God is very compassionate when you lose someone close like that. He will certainly try to bless you out of that loss when the time is right. Am alternative that helped me too was to consider foreign women.
I am certain the whole ordeal is like a test to you, with all kinds of emotions and thoughts. Rather than having even a hint of blaming God, which you may or may not be doing, you have to dig deep and let the relationship serve to inspire you to do even greater things for God. That death in my life inspired me to become a Christian, to this day, decades later, it continues to help me care more about others. I pray her death will be a positive catalyst for you too in every way, including marriage if you find the right person. God bless.