It really hurts when the just up and walk out, been there.
Just go on being you thats about all you can do.
My fist wife walked out too but I kept my kids I'm thankful that she had enough sense to know I was stable and a very good Dad.
I still hate her guts just not as bad now.
I was left twice for another man that really hurts.Sounds like that is what she did to you. When they say friend it means a man no matter what they say take it from me if she did that to you you are better off without her IMO.
Be strong sis.