I understand exactly how you feel. First, don't push her anymore. Last month, my H. made a comment to me about how o.w. didn't push him for a decision, and he felt that I did. He said, "It's not like you are saying, 'take your time with this.'" See, they want time, and space. Give it to her.
She also repeatd that she loves me and that she know our marriage can't go on witht as long as she has these other feelings for the OM. Yup, have heard this too. My H. said his "mind is elsewhere" and he cannot come home while he has a gf. That he would rather take the chance than wonder about it. Nothing I can do about his choices...if that's what he really wants to do.
Most of us really marry only once. First love endures, even unto our dying day. And we never really divorce.