Sorry to hear about your situation Pantheist. You said that your wife was Mono from the start. Well, much as she got into a poly relationship with you, you got into a mono relationship with her. Lemme try and explain.
While she was with you, who was poly and with others, she herself never had the experience. You said that she was young and inexperienced with relationships. Remember that in her world all she was taught was that she would find the right guy and settle down and have 2.5 kids with a house and a white picket fence. Even though she didn't find all of that with you, when your other partners faded out of the picture and it was just you and her, I'm sure her mono wiring kicked in and she figured she got what she was looking for anyway.
She's never had the need to even begin to change the way she thinks because she's only been with you. You have experience with the lifestyle so you understand that it's very possible to be in a loving, fulfilling relationship with more than one person. She doesn't know that yet.
Has she done any research on the poly lifestyle? Maybe she should come here and see what it's all about. Get a feel for things on her own.
Good luck and keep us posted.
Live life to the fullest 'cause you never know if you're gonna wake up tomorrow!