Instead of sulking about what you lost think about what you gained. The fact she did this now instead of you guys getting married and having to deal with a divorce and possibly kids fucking up other lives. She did you a huge favor that some people don't get until it's too late. Take it from me. My brother is going through a divorce and he's going to end up bankrupt from the lawyer fees but he'd rather lose all his money to his lawyer then give her a single penny.
I do try and think of this often. Being an optimist (which comes off as desperate at times, as shown here...)it's a difficult task to envision an even more negative outlook, as the one you mentioned.
But.
It's so very true.
The head and the heart do not align. That's the main issue.
Emotions outweigh the logic of it all.