I'm sorry for what you are going through. I've been betrayed, abused, mistreated for much of my life.
The best thing I can come up with, is to be kinder to yourself, learn to accept your faults, realize that the "best" human beings can make horrible mistakes and really hurt others like yourself.
You are blaming yourself for having introduced them to each other. It is just what happened. She might have gotten introduced to someone else and left you for that person. She made the mistake of hurting you.
I've struggled for years to get over my marriage, and it wasn't a good one. I've used up boxes of kleenex, felt so down and low I thought of suicide, it is really damn hurtful when others treat us like we aren't worth anything
NOW is the time to stop letting that happen. Start with YOU, what things (however small), you enjoy right now? I know you are thinking, "nothing"...
I've learned at times the suffering overtakes any joy. But start small. Favourite drinks, books, music, making sure you are sleeping well, getting some fresh air.
Best wishes, and if you ever want to talk, you are welcome to p.m. me if I can be of any help.