As much as I like to think of myself as being open-mined toward open-relationships if that's what both partners want, I can't say I've ever heard of a situation where it's actually served as a fixer for a broken monogamous relationship. Nor have I ever heard of a case where one partner stops wanting to bone the other, begins an open relationship, and the open relationships brings their desire to bone their partner back from the dead.
What I'm thinking is that she wants to have her cake and eat it too - she wants to play the field but she doesn't want to lose the security blanket that she has with you in order to do so, she wants you to be there for her to fall back on just in case ****ing around doesn't work out or isn't as glamorous as she thought it would be. And if I'm right then allowing her to play that game would be enabling behavior which is going to teach her not to respect you. She will know that she can't lose you - you will always be there no matter what she does and thus you will lose value to her.
On the other hand, you can try to convince her to remain monogamous with you or issue an ultimatum or whatever but after she expressed desire to bone other people AND expressed that she no longer has any desire to bone you...those two things combined lead me to believe that if she hasn't cheated already she will.
Sorry OP but I think this one is just about over.
They see indoctrination and they call it "morality", "professionalism", or "maturity" depending on the context.