Let me clarify. When I say have the conversation and ACCEPT THE RESULT? I mean stop pushing. Pointing her to resources to educate on poly is one thing. Then she can make her decision from a place of information and not ignorance if she wishes to read more.
Pushing "Let's try it!" when she has no enthusiasm or desire for it is another. Her body, heart, mind, soul BEING is HERS to share as she sees fit. NOT YOURS. So back off on that. You do not own her any more than she owns you.
If you have the conversation and she says she does NOT want to go there? Accept she does NOT want to go there with you.
And if you are at this place?
I have changed/grown into this, and she either comes with me, learns to compromise or tolerate it, or we do have to go our separate ways.
Then JUST END IT. Stop peddling the idea and stop peddling the "aw c'mon... give it a try!" It flat won't work. Don't be a pushy poly person.
End it fast and clean and ethically. Stop dragging out the misery for both of you. Move on toward future happiness instead of beating a dead horse.
It's cruel/unkind to keep on and on that way. Accept this is a basic mismatch and end it. See if you can be good exes and leave it at that.