Answer
As-Salamu `Alaikum Brother,
Falling in love before marriage often results in such emotional roller coasters and disasters. But, unfortunately, love just happens. What needs to be done is to carefully consider all the probabilities of bringing this love as quickly as possible into the realm of halal and legitimate relationship. Until then patiently pray to Allah (swt) to protect you both from falling prey to the evil of your nafs (soul) and Shaitan.
Now, in your case, the young lady no longer wants to marry you and has accepted the proposal of another man. I don’t know what emotional and family circumstances have she chosen to do so, but it is important for you to understand that:
1) Relationships can only work two ways.
2) Regardless of how much you love her, if she does not want to be married to you, you have two choices: either to sulk and feel sorry for yourself and be angry at her, or count your blessings and move on. It is better now that she dropped you rather than after marriage, isn’t it?
I know it is easy for me to say this, but it would be difficult for you to do because of the intensity of your emotions. But, ultimately, this is what would help you put back on the path. Hopefully, it will mature you and give you wisdom for the future.
Get up, pack up, and move on. There is nothing you can do about the spilt milk, and it is not wise to insist that you only want to lick back the split milk.
May Allah help you!
***
Disclaimer: The conceptualization and recommendations stated in this response are very general and purely based on the limited information provided in the question. In no event shall AboutIslam, its counselors or employees be held liable for any damages that may arise from your decision in the use of our services.